My phone has 4G but at&t claims it is only a 3G phone
Hi i received a txt that my Oneplus 7t phone will no longer work after February 2022, but it is on the "list of phones that will still work on your network". And I had and still can use 4G LTE on the 7t phone. I bought the phone back around November and never had a problem with it, until I had broke the screen and replaced it. While I was fixing the screen on my OnePlus 7t, I had put my SIM card back in my old phone so I could still be in contact with people. And did it with no problem. When I put the same SIM card back into my 7t I got a txt from At&t saying my phone is no longer compatible with my SIM card, and that my OnePlus 7t phone was not a 4G phone. Can you help explain why my phone is not a 4G phone, and why it will be getting kicked off the network?