Nokia 7.2 Strange Behavior neither here or there - Nokia 7.2 Questions & Answers

Back in March, purchased four new Nokia 7.2 phones for the family. Moved the Sims from old to new devices and activated them through my carrier, and all was working fine with all four phones.
Then today, one of them, one that belonged to one of my kids, started behaving really oddly. I should say, some other things started a few days earlier, like some mmorpg aps started telling my kid to use device he made account with, which is what they were doing when trying to log in.
Today, it got stranger. Went to send my same child to a party using my AP to buy the ride and send it to my kids phone. My side showed it was working, but my kids got no notifications what so ever, so made a share link, and sent that which worked.
Once AP showed me they got to their location, waited for the call which was a system we set up to verify they got to where they were supposed to. Call didn't come, which was not normal, so called their phone and also sent a text message. Phone rang and rang first time with no one picking up. Figured maybe they got absent minded, as they were at a party saying bye to their best friend who was moving from the USA. So tried again, to have someone answer who was obviously very angry, and yelled in a language I still have no clue, and then hung up. I immediately believe either they are in trouble, or had their phone stolen, so call their friend who hands my kid their phone and my kid tells me, he tried calling me, but call would not work, just total silence so they called my wife instead to say they were ok. My kid also tells me they still have their phone and it's been on them all this time, so no clue how someone else could have answered their phone.
I decide to try something, and log into my account as all 4 phones are registered to me, and go to see where their phone is located, but was unable to as their phone did not show up, only the other 3 did.
I then try something else and log directly into my kids account to try same thing, except doing so, caused the application to lock up almost every try.
When I finally did log in, did a location find, and every time map refreshed, it either showed my kids location or jumped outside the USA map and locked up. I try making phone ring, a few times, which resulted in getting two text messages in a foreign language with characters I never seen. I even noticed that the two pop up messages were not even in the mms text message ap.
Shortly after, my kid calls me to say his phone location ringer went off once, and wanted to make sure it was me. Only once, out of 6 or 7 tries.
After they got off, their phone showed up on the other account where it was missing earlier, and the location stayed now where my kid was. When they got home, checked the parental so, and saw only one location ring was recieved.
Is their something new, that allows someone to steal services off ones phone? Makes me wonder if we got a used phone.
Reminds me of a neighbor who got arrested for many break-ins several years ago. They would break into homes and steal what people wouldn't miss, but stupidly got caught because the idiot who broke into our house and stole an old tablet packed up in our garage, was only a house down from mine and close enough to connect to our asus router. When I saw the request to connect by a device that should be dead after 4 years boxed up, did a gps and not only shocked to see it in my neighbors home, but the amount of times they went back and fourth between not just our home, but other neighbors as well. Pd was going to call it a civil matter, but quickly changed when I activated the very loud siren sound I had saved as a location ringer. Look on their face was priceless. Anyways, not sure if getting a new sim is in order, or just make the seller replace the phone in question as the whole mess with my kids phone is baffling.