US T-Mobile with EU Honor 8X - Honor 8X Questions & Answers

I am about to blow my brains out with this one.......
Guys just a quick question if possible. I got this Honor 8X unit, a JSN-L21 and according to gsmarena this device not only has GSM but also CDMA. All I am trying to do is to use it with T-Mobile or ATT and have LTE on it.
So I tried BYOP with T-Mo and they're saying that this unit doesn't have VoLTE ..... well I don't know about that and I can't believe that 2018 phone doesn't have that. But again I don't know. And ATT refuses to work with it period, showing no service or emergency calls only. What a hell is going on I tried to read on it and almost flashed it with like LineageOS but then I find out bootloader is locked and the company no longer unlock them. If you can please let me know what a hell is going on. Is it like EU only phone or something? Why it's not connecting to LTE and no working with one of the 4 Major US telcos.
Thanks, guys, please help cause I am clueless with this Huawei brand.
Here is complete info on the phone in question:
Description: Honor 8X 4GB+128GB Blue Dual Card Open Market Ver. France
Model Code: Johnson-L21D
IMEI: 86577704526xxxx
S/N: 9YHNW18B2300xxxx
IMEI1: 86577704527xxxx
MEID HEX 14: 8657770452xxxx
IMEI: 86577704526xxxx
MEID HEX: 86577704526xxxx
WIFI: 3412F9AE1xxx
MAC: 3412F9AE1xxx
Item Code: 51092xxx
Customer Code: 100158xxx
Offer Code: OFFE00067xxx
Company: TECH DATA FRANCE
Country Code: FR
Country Name: France
Warranty Status: In Warranty
Warranty Start: 2019/1/28
Warranty Expire: 2021/1/29
Warranty Details:
Warranty Type: 2 Year Warranty
Valid in Country: AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LT LU LV MT NL NO PL PT RO SE SI SK
Service Code: BS03000xxx
Start Date: 2019/1/28
End Date: 2021/1/29
Bind Date: 2019/5/19
Order Date: 2018/11/23
Shipment Date: 2018/12/6
Delivery Date: 2018/12/11
Activation Date: 2019/1/28
Warranty Type: 14 Day Device Return
Valid in Country: FR
Service Code: BS01000xxx
Start Date: 2019/1/28
End Date: 2019/2/11
Warranty Type: 14 Day Device Replacement
Valid in Country: FR
Service Code: BS02000xxx
Start Date: 2019/1/28
End Date: 2019/2/11

---

AT&T uses bands 2, 4, 5, 12, and 17; the L21 has 1, 3, 5, 8, 38, 39, 40, 41. At best you would have band 5 for 4G, and that's only if you were in an area with band 5 coverage. AT&T 3G uses 850 and 1900, but the L21 only has 850.
T-mobile uses 2, 4, 5, 12, 66, and 71 for 4G, and 1900 and 1700/2100 for 3G.
An L23 would work with either carrier as it has 1, 2, 3, 4, 5, 7, 28, and 41, as well as all the 3G bands for both carriers. I have an L23 on Cricket (AT&T) and it works great.