I lost countless hours looking for an answer and still looking how to fix it.
after I rooted my SG2, the mobile wireless has no bars, checked to see if was the sim card, and is not as I have tested on my gf htc hero, and works fine.
I have then unrooted to see if the problem would go away
and is still with no signal when I try to call someone says
mobile network not available
here's the stats
About Phone
Model number
GT-I9100
Android Version
2.3.5
Baseband version
I9100BUKI1
Kernel version
2.6.35.7-I9100XXKI3-CL577579
[email protected] #2
Build number
GINGERBREAD.BUKJ3
I have first rooted with
CF-Root-SGS2_XW_XEN_KJ3-v5.0-CWM5.tar
then have unrooted with
Kernel_I9100XXKI3.tar
my wireless network provider is giffgaff
I can't call receive calls or message anyone
and before was working just fine
Please Help
thank you
Plutonian32 said:
I lost countless hours looking for an answer and still looking how to fix it.
after I rooted my SG2, the mobile wireless has no bars, checked to see if was the sim card, and is not as I have tested on my gf htc hero, and works fine.
I have then unrooted to see if the problem would go away
and is still with no signal when I try to call someone says
mobile network not available
here's the stats
About Phone
Model number
GT-I9100
Android Version
2.3.5
Baseband version
I9100BUKI1
Kernel version
2.6.35.7-I9100XXKI3-CL577579
[email protected] #2
Build number
GINGERBREAD.BUKJ3
I have first rooted with
CF-Root-SGS2_XW_XEN_KJ3-v5.0-CWM5.tar
then have unrooted with
Kernel_I9100XXKI3.tar
my wireless network provider is giffgaff
I can't call receive calls or message anyone
and before was working just fine
Please Help
thank you
Click to expand...
Click to collapse
Flashing a kernel shouldn't have done this. Sounds like you either flashed a firmware package that included modem files for a different carrier, or accidentally flashed a different modem, which isn't for your carrier.
Do you know what other carriers are compatible with giffgaff?
Is your firmware carrier branded? I would just flash the latest available firmware for your carrier if it is branded, or if not branded, KI3 or newer from the unbranded thread.
Carrier branded firmware thread is here.
Unbranded firmware thread is here.
dude i post a thread were you dont need to flash anything in order to have root reed this post http://forum.xda-developers.com/showthread.php?t=1321538
MacDrunk said:
dude i post a thread were you dont need to flash anything in order to have root reed this post http://forum.xda-developers.com/showthread.php?t=1321538
Click to expand...
Click to collapse
It's a little late for that. His problem now is not getting root, but getting his phone working again. I suspect he'll have no choice but to flash SOMETHING to get it functioning again.
I have used odin 1.85
then I rooted with this
CF-Root-SGS2_XW_XEN_KJ3-v5.0-CWM5
I have not done anything else
and I have no signal inside my house
when I go outside I have signal, but is not the sim card, and was working before
this is doing my head in
my carrier is giffgaff
the phone is unlocked and giffgaff runs on O2
You want to set up network .
Use the GiffGaff Tools/Apn app from the market or Giffgaff forum.
Giffgaff will work as O2 PAYG if not set .
You say Mobile wireless do you mean WiFi if so nothing to do with GiffGaff try flash a different modem .
Root should not have caused a problem .
Are you sure you have a i9100 .
and I have no signal inside my house
when I go outside I have signal,
That is simply the network your house is blocking the O2 signal .
you can check your nearest O2 base station
http://www.sitefinder.ofcom.org.uk/search
jje
Is not the Wifi, wifi is working.
ke a call receive calls
I use to have 3 bars inside my house now after rooted have none, and can't even make/receive calls or msgs inside my house, outside have full bars,
I think its the weirdest thing I ever seen.
Please help
Plutonian32 said:
Is not the Wifi, wifi is working.
ke a call receive calls
I use to have 3 bars inside my house now after rooted have none, and can't even make/receive calls or msgs inside my house, outside have full bars,
I think its the weirdest thing I ever seen.
Please help
Click to expand...
Click to collapse
You have a choice
One flash a modem from the modem thread .
Two flash full original stock rom from stock rom thread that will remove root .
Three ask the network is their work on the local transmitter .
Four ask the network to move the transmitter to your kitchen .
Why did you root ???
What is your current modem ??
jje
I rotted because I use to have an ipod touch and I jailbroke it, and I could get all paid apps, and just really curiosity
in my case curiosity killed the phone
where do I find the modem model/number on my phone?
I have rooted again using odin 1.85
and have this now
CF-Root-SGS2_XW_XEN_KJ3-v5.0-CWM5.tar
still back on square on, I'm waiting for my samsung class 10 32GB micro sdhc card, so I can back all my data from the 16Gb card, and format it,
and try to restore to factory settings if I can
as it came out of the box
not sure how will i do that, but if you can help me, that would be great
thanks
Plutonian32 said:
I rotted because I use to have an ipod touch and I jailbroke it, and I could get all paid apps, and just really curiosity
in my case curiosity killed the phone
where do I find the modem model/number on my phone?
I have rooted again using odin 1.85
and have this now
CF-Root-SGS2_XW_XEN_KJ3-v5.0-CWM5.tar
still back on square on, I'm waiting for my samsung class 10 32GB micro sdhc card, so I can back all my data from the 16Gb card, and format it,
and try to restore to factory settings if I can
as it came out of the box
not sure how will i do that, but if you can help me, that would be great
thanks
Click to expand...
Click to collapse
Type *#1234# into the phone pad and what is shown against PHONE is your modem number.
As the previous poster suggested I suspect that you have inadvertently changed your modem. I am on Giffgaff with the original O2 firmware on the phone. The modem for this is XXKI4. I understand that the previous modem was XXKI3.
You can download one or both of these modems from
http://forum.xda-developers.com/showpost.php?p=17967764&postcount=5
Please read carefully what it says. i.e. The zip files are intended to be flashed from your internal or external sd card using clockworkmod (CWM) recovery (you have this as you rooted a CWM kernel) and should NOT be flashed using ODIN. If you want to use ODIN then you can extract the modem.bin file from the zip and flash that from the PHONE section of ODIN.
Hope this is of some help.
Pda: I9100xxki3
phone: I9100xxki3
csc: I9100oxaki3
built info: Thu sep 15 13:53:07 kst 2011
used Odin with moden.bin
xxki4
when I click search networks
heres the options
T-Mobile UK
Orange
3 UK
Vodafone UK
theres no O2
or Giffgaff,
PDA:I9100XXKI3
PHONE: I9100XXKI4
CSC: I9100XAKI3
BUILD INFO: THU SEP 15 13:53:07 KST 2011
still same problem no networks available
can't call or receive calls or messages
inside my house
Plutonian32 said:
used Odin with moden.bin
xxki4
when I click search networks
heres the options
T-Mobile UK
Orange
3 UK
Vodafone UK
theres no O2
or Giffgaff,
PDA:I9100XXKI3
PHONE: I9100XXKI4
CSC: I9100XAKI3
BUILD INFO: THU SEP 15 13:53:07 KST 2011
still same problem no networks available
can't call or receive calls or messages
inside my house
Click to expand...
Click to collapse
When I search networks I do get O2 in the list. You wont get Giffgaff as it's not a network but uses O2's.
It may be that for some reason O2 are putting out a weak signal in your area. If your phone is unlocked have you tried sims from other networks to see if you get the same drop off between inside & outside the house. If you do then it would suggest it's the phone (hardware or firmware) but if you don't or the drop off is much smaller then it might just be an O2 signal problem. If you know someone who has an actual 02 sim then perhaps you could try that as well.
I know is not the Sim card, as my gf uses giffgaff as well and I tried on her HTC hero, and has 3 bars, works fine.
I just don't understand why when I rooted the phone the phone network coverage inside my house went to nil, and when I get outside my house and around town I have full bars and 3G is working, I only able to use my WIFI inside my house and Bluetooth.
which is a Pain in where the sun don't shine, because how am I spose to receive calls or call anyone in the comfort of my Home, impossible so people will be thinking that I'm ignoring them, or think I'm rude.
I will try other sim cards and see if that will be the problem.
thank you
you been very helpfull, will report back later
I sometime have this problem all i do is restore efs back using ktool. If you made efs backup using hc-ktool try restoring that and reboot. Your mobile signal will start working again.
Sent from my GT-I9100 using xda premium
I don't think I have made a backup,
I'm not familiar with Ktool
just know how to work odin 1.85
Plutonian32 said:
Pda: I9100xxki3
phone: I9100xxki3
csc: I9100oxaki3
built info: Thu sep 15 13:53:07 kst 2011
Click to expand...
Click to collapse
I've just noticed that you've put down your CSC as I9100oxaki3. Is this correct? Because I think OXA is a country code for Poland. If it is then perhaps you flashed a firmware intended for Poland. I don't known whether this difference in CSC setting would affect your signal. I'd always thought that the call side of things was handled by the modem and the XXKI4 modem is definitely UK compatible. I may be wrong though.
If nothing else is working then perhaps you could try flashing a firmware with a CSC that is UK specific, includes the UK or is generic European. Post #2 has a link to available firmwares.
I am not sure what suggest then. When i rooted my phone first thing i read was to backup efs using ktool which can be downloaded from market. Then i used cwm manager to backup stock rom. Check in your sd card if have efs folder if yes download ktool and use an option to backup efs and restore using the tool it will ask you if you want to restore by .tar method choose that. It all depends if your phone has efs folder and files init.
Sent from my GT-I9100 using xda premium
As a relatively small network GiffGaff may not be in older or even newer CSC network lists /
Use GiffGaff APN tool .
OXA is Poland
You do not need a CSC to use the phone GiffGaff settings either manually or via the GiffGaff tool
jje
I fixed the Phone, finally,
it has 3 bars now and its the way it was, but I lost all my settings, easy to fix though.
heres my new info
Version
PDA: I9100XXKI3
PHONE: I9100XXKI3
CSC: I9100XAKI3
Build Info: Thu Sep 15 13:53:07 KST 2011
I'm not sure if its rooted or is flashed back to stock what I did was
use odin 1.85
tick - re-partition, auto-reboot, F.reset time
PIT - u1_02_20110310_emmc_EXT4.pit
Bootloader - GT-I9100_OLD_BOOTLOADER.tar
PDA - CODE_I9100XXKI3_CL577579_REV02_user_low_ship.tar.md5
PHONE - MODEM_I9100XXKI3_REV_02_CL1062028.tar.md5
CSC - GT-I9100-CSC-MULTI-OXAKI3.tar.md5
and clicked Start
and after that, was set to factory reset as it came out of the Box
It did not delete my software that I had on my internal 16Gb, but is not active
so I have to re-install the apk again, and add contacts from my facebook and google account.
O2 network appeared I registered on that and I set my apn for giffgaff and is all up and running, thank you so much for all your help, anyone around newport area, I'll buy a Beer
thanks
David
Bought a galaxy sII
second hand
(well swapped iPhone4 for it)
however the amount of problems it has is honestly unreal and its one step from going through the window!
It goes from 100%-30% when it feels like it , and powering it off results in an overheating indicator ( yellow thermometer triangle )
and unable to turn on without going via: VOL UP+HOME+POWER
its come to the point where I need to just get it replaced under warranty.
however its been updated to ICS and i have no idea what was originally on the handset. i THINK its a Vodafone UK handset - but rooted and unlocked, therefore i need to try and figure what it would be on had it never been upgraded/rooted/flashed.
ill try post as much stats etc here as i can in hope that will make things clear to see what my problem is.
CURRENT:
PDA: I9100XXLPQ
PHONE: I9100XXLPQ
CSC: 19100 OXALPQ
BUILD INFO: FRI MAR 9 01:58:19 KST 2012
**********************************************
I have no idea how to get it back to original software etc
( I'm an apple guy to be honest )
PS: ORDERED USB JIG TO KEEP WARRANTY VALID TOO - SHOULD I HAVE ANY LUCK GETTING IT ALL READY TO BE RETURNED.
Thanks guys!!
Leon
Use the PC version of Checkfus to determine what firmware was originally on the phone (you enter the phone model/carrier/country & the software will tell you original firmware), then search Samfirmware.com for it. Flash the firmware following whatever instructions they have for flashing firmware downloaded from their site.
OR
If you're happy with the latest firmware available for your carrier/country (may or may not be the original firmware which came with the phone dependant of whether carrier has issued firmware upgrades since), you can use Checkfus to download same. If you go down this route, flash the tarball you download following instructions here.
Afternoon all.
I need some help. I have been searching forums all day trying to find a solution to my problem, but I'm just getting more confused. So please, if there is someone out there that can help, I would be grateful.
Bit of background. Yesterday, my phone was working correctly and when I went to make a call later in the day I had no network. When I tried to check the network settings, it stated "Insert SIM card to access network services".
When I checked Settings>About device the Baseband version is listed at "Unknown"
I read somewhere to try *#06#, which I did and it shows IMEI/MEID "null / null"
My phone is a Galaxy S2 GT-I9100 on UK Vodafone network, the rest of the phone info is as follows:
Android version: 4.1.2
Baseband version: Unknown
Kernel Version: 3.0.31 - 462349 [email protected] - 111 #3 SMP PREEMPT Tue Nov 6 02:42:23 KST 2023
Build Number: JZO54K.I9100XXlSJ
I have already tried the following:
1. Removed battery, waited 10 minutes, rebooted - Failed.
2. Wiped data and factory reset - Failed.
3. Installed a completely new version of 4.1.2 from HERE - Failed.
4. I have also tried my SIM card in my misses GT-I9100 and it works fine, so it's a handset issue.
I am at a loss of what else to try.
Can ANYONE help me, please!!!
Thanks in anticipation.
Pete.
If you've never 'messed with' the phone (rooted it or run non-stock firmware), send it in for warranty service if your warranty is still good. Trying something that could potentially bork that warranty & end up costing you money isn't worth it, and there's a fair chance they wouldn't work anyway unless you had an EFS backup which you wouldn't have if you've never rooted your phone.
Peteinhull said:
....
Click to expand...
Click to collapse
The rom you linked to is the older leaked pre-public version of Sammy JB. You should try flashing the latest final public version from here.
You need to flash another modem ... Tell me if it works or not
Or try this
http://forum.xda-developers.com/showthread.php?t=1264021
Sent from my iPhone using Tapatalk
I have the same problem with me & I also tried the above methods but failed every time I also changed the sim slot but failed
Hi Guys,
2 months ago I bought a Samsung s5 in Hong Kong.
While travelling through South East Asia this device worked fine.
While traveling through New Zealand (Old home) this phone worked fine.
While traveling through America (New Home) this phone worked fine for the first 2 weeks (on the metroPCS network).
The problem:
Randomly after 2 weeks the s5 stopped connecting to the metroPCS mobile network even though the network was available (btw metroPCS uses the T-Mobile network). It gives errors such as network not available or cannot register with network.
Things I have tried:
-Im sure the APN settings of the phone have not changed and I have double checked to see if they are correct.
-replacing the sim card with another does not fix the issue
-soft and hard reset of the phone does not fix the issue
-Getting metroPCS to refresh the service on this number does not fix the issue
Other important info:
-This phone was purchased in hong kong but it is from the Philippians according to Kies's firmware information (XTC is the country code)
-It is running a custom allianceROM that must have been installed by someone in hongkong
-The device is rooted (superuser app installed)
-the model number as shown in settings is g900f BUT when attempting to flash with odin the phone displays g900t and fails to flash the latest Philippians verison of kit-kat
I have 2 questions:
1. Any ideas why my network connection has suddenly self destructed (and how to fix)?
2. Would flashing a stock ROM to my s5 help? and if so why is there conflicting information on which model I own (g900t/g900f)?
Please help. I do have some know how on flashing android devices but i've really hit the wall on this one guys!
Cheers,
Yetti.:cyclops:
It's not uncommon for the model # to be different with a custom rom as that is a very easy thing to edit in the build.prop. It should tell you under the battery which one it is. As far as the network issues, check to see if the baseband and IMEI are still there and not listed as unknown or incorrectly. It's possible you could get away with flashing the appropriate modem that matches with your update and that might work better in this region vs the previous one.
Please list the Alliance rom version and baseband version here in case it's relevant to your issue.
More info
Im not sure if this helps but looking through the build.prop file in the system folder my ro.product.local.region=GB
When in recovery mode the region is set to XTC (Philippians) using mutli-csc.
Also my IMEI number seems ok and is NOT blocked.
Cheers. Yetti :cyclops:
Baseband and rom etc
Thankls for your reply!
Sorry when you say "under the battery symbol" do you mean in /odins boot script on the device/ or /in settings on the phone/?
Baseband is g900TUVU1ANCH
Build Num: AllianceROM_G900F_XXU1ANCF
If the "no network" issue can be solved with the current firmware that would be the most desirable solution but going through the flashing process may be a good idea for my learning process, and will help with future updates.
Do you think getting back to a stock rom would help me?
tHANKS AGAIN!:cyclops:
Model confirmed to be g900t
Sorry i didn't understand the "under the battery" thing. I was lost in software world. The sticker under the physical battery says SM-900T so i guess that confirms that it is a t-moble verison (and the baseband is therefore correct).
I will try to flash the T-Mobile stock image to the phone and see if that works.
Also i will try to flash a modem (after i work out which one i need).
Cheers, Yetti :cyclops:
Current status.
Flashed the stock T-Mobile firmware to the phone. No success.
Flashed new modem to the phone. No success.
Will go to the T-Mobile store tomorrow to see if they can help (I doubt it but i have to exhaust all the options).
Any more help would be appreciated...
cheers, yetti:cyclops:
By under the battery I mean like to take off the battery cover of the phone and pull the battery out and look at the sticker found there.
G900t.
es0tericcha0s said:
By under the battery I mean like to take off the battery cover of the phone and pull the battery out and look at the sticker found there.
Click to expand...
Click to collapse
Yep it says g900t (see above)
As per flashing a modem. I have heard that it is possible to flash any modem for any version of the s5 to the phone. Some work well and others not so much. I have tried 2 T-Mobile modems (baseband) the G900TU1ANCH and the G900TUVU1BNG3 with no success. Do you have any recommendations for a modem to try (or even a custom ROM that might help?)
Cheers,
Yetti :cyclops:
I know that you mentioned they refreshed the service for your number, but do they have the correct IMEI in the system for your account? Metro makes a big deal about that now and you can't just take your SIM from another phone and pop it in a new one and go like you can with pretty much every other service (Cricket is like this too now).
I bought a s9+ from swappa around February. I bought my mom one from the same supplier a week ago. At first I was concerned that her's had ATT logo until I realized it would change once a tmobile sim was put in. Her's is now SW ver Tmb/Tmb/Tmb. Then I noticed she is at Android 10.0 UI ver 2.0. I am stuck at Android 9 UI ver 1.0
So It seems I was worried about the wrong phone. It is MY phone that can't get updates. My baseband is:
G965USQU7CSK6 which I believe is an ATT baseband. my SW ver is Tmb/Tmb/Att
I tried connecting to smart switch and it says I am up to date. I tried putting in an at&t sim card (that no longer is in service) and smart switch doesn't complain about anything but it still says it is up to date. Doing OTA while using At&t sim card also says I am up to date. I am CLEARLY not up to date. My last update says Nov.1, 2019.
I have used Odin before...mostly for rooting phone. I haven't rooted since the s5 ( where I could take the battery out ). Little paranoid to use Odin considering I can't take the battery out, but with good instructions I will proceed.
Any help on how to update and especially update on tmobile network would be extremely appreciated.
btw I'm in the US and my model is SM-G965U
-Craig
--UPDATE
I have researched a bit and found that it IS possible to change the firmware over to Tmobile using a patched version of Odin.
I downloaded from
https://forum.xda-developers.com/android/software/patched-odin-3-13-1-t3762572
the 3.13.3_3B_PatcheD.zip
I downloaded G965USQS7CSK3_G965UOYN7CSK3_TMB.zip
from sammobile, which is for Android 9
I would love to be able to use HOME_CSC but that may not work. I could really use some hand holding going through this process.
Is this the correct firmware? Should I be using Android 10 firmware if that is ultimately what I want? HOME_CSC or no? I notice they have the 10 version:
PDA G965USQS7DTB1
CSC G965UOYN7DTB1
as well, which is Android 10 for Tmobile. Also, knox ? will this trip the knox counter thing-a-ma-jig?
Thanks
SOLVED
cw9002 said:
I bought a s9+ from swappa around February. I bought my mom one from the same supplier a week ago. At first I was concerned that her's had ATT logo until I realized it would change once a tmobile sim was put in. Her's is now SW ver Tmb/Tmb/Tmb. Then I noticed she is at Android 10.0 UI ver 2.0. I am stuck at Android 9 UI ver 1.0
So It seems I was worried about the wrong phone. It is MY phone that can't get updates. My baseband is:
G965USQU7CSK6 which I believe is an ATT baseband. my SW ver is Tmb/Tmb/Att
I tried connecting to smart switch and it says I am up to date. I tried putting in an at&t sim card (that no longer is in service) and smart switch doesn't complain about anything but it still says it is up to date. Doing OTA while using At&t sim card also says I am up to date. I am CLEARLY not up to date. My last update says Nov.1, 2019.
I have used Odin before...mostly for rooting phone. I haven't rooted since the s5 ( where I could take the battery out ). Little paranoid to use Odin considering I can't take the battery out, but with good instructions I will proceed.
Any help on how to update and especially update on tmobile network would be extremely appreciated.
btw I'm in the US and my model is SM-G965U
-Craig
--UPDATE
I have researched a bit and found that it IS possible to change the firmware over to Tmobile using a patched version of Odin.
I downloaded from
https://forum.xda-developers.com/android/software/patched-odin-3-13-1-t3762572
the 3.13.3_3B_PatcheD.zip
I downloaded G965USQS7CSK3_G965UOYN7CSK3_TMB.zip
from sammobile, which is for Android 9
I would love to be able to use HOME_CSC but that may not work. I could really use some hand holding going through this process.
Is this the correct firmware? Should I be using Android 10 firmware if that is ultimately what I want? HOME_CSC or no? I notice they have the 10 version:
PDA G965USQS7DTB1
CSC G965UOYN7DTB1
as well, which is Android 10 for Tmobile. Also, knox ? will this trip the knox counter thing-a-ma-jig?
Thanks
Click to expand...
Click to collapse
ok, so I bit the bullet and decided to go ahead. I used
odin 3.14.1_3B_PatcheD.zip just to be sure
I made sure my phone was unlocked: yes it changes carriers if I put in different sim. When in Tmobile sim Settings->Connections->Mobile Networks->Network operators , yes it has a search networks button and it eventually comes up with other carriers so....safe to say I had unlocked phone ( but not samsung unlocked ie. SM-G965U not SM-G965U1)
I used the latest android 9 firmware. and I used HOME_CSC ( even though I did a backup with smart switch b4) Everything went smoothly, and I still have my apps and now I can get an ota security patch for it. Will write back once I am up to Android 10. oh, btw I am still at SW ver Tmb/Tmb/Att , but I've got ota updates so I don't care
cw9002 said:
ok, so I bit the bullet and decided to go ahead. I used
odin 3.14.1_3B_PatcheD.zip just to be sure
I made sure my phone was unlocked: yes it changes carriers if I put in different sim. When in Tmobile sim Settings->Connections->Mobile Networks->Network operators , yes it has a search networks button and it eventually comes up with other carriers so....safe to say I had unlocked phone ( but not samsung unlocked ie. SM-G965U not SM-G965U1)
I used the latest android 9 firmware. and I used HOME_CSC ( even though I did a backup with smart switch b4) Everything went smoothly, and I still have my apps and now I can get an ota security patch for it. Will write back once I am up to Android 10. oh, btw I am still at SW ver Tmb/Tmb/Att , but I've got ota updates so I don't care
Click to expand...
Click to collapse
I am now at the same baseband version as my mom. Everything worked perfectly. I suggest you go with the least change possible to get to the point that you are able to do OTA updates. For me this was going to the latest Android 9 that they had at sammobile since I was on Android 9 and going with the Tmobile version. I hear the carrier doesn't even matter these days, but I decided I wanted to make sure it was Tmobile compatible so I chose the Tmobile version from sammobile. Happy trails to you in your endeavors. Hopefully you can learn something from mine.
Hey, I really want to thank you for this! I had the same issue and was exploring similar solutions. After several days of researching alternate plans, I was about to give it up as too risky until I found your post - by googling for hints: "SW ver. TMB/TMB/ATT"! You helped me take the dive, and I'm now happily past having a second-hand S9 (sm-g960u) that wouldn't do an OTA update. After a flawless flash, my first OTA request got me to Android 10, (UI 2). now I have a follow-up update scheduled for the wee hours. (And, yes, I'm still at "TMB/TMB/ATT".)
Perhaps like you, I started by investigating the possibility of flashing the UNLOCKED ("U1") firmware. After learning it was possible with the _patchedD Odin, it still scared me enough that I decided on a more conservative approach and followed your exact advice. I especially appreciated your plan to flash NOT the latest update, but the last Android 9 TMB update. That turned out to correspond to the ATT version on my phone, making TMobile either unable or unwilling to offer an OTA update.
History: This is my third used S9. While all were sold as UNLOCKED, only the first had the "U1" model suffix (SM-g960u1). When the second one booted up as a TMobile phone, I felt tricked - but also lucky that I got the right carrier. That's when I learned about the difference in model numbers. As you noted the U1 firmware is factory unlocked - attached to no carrier. When my third phone booted up with a Verizon greeting I figured I could be facing trouble - even though it accepted my TMB sim card.
The seller explained to me that my phone was part of a batch of ATT phones, all "SIM unlocked" using a Verizon sim card. I think sellers of phones with claims to be unlocked should be required to specify whether FACTORY or SIM unlocked.
Hope this great contribution of yours will continue to help others.