The end of 3G is coming for every carrier, but the way AT&T is handling their 3G shutdown is rubbing some people the wrong way.

AT&T has chosen to go with a specific allowlist of devices that can continue to connect to their network following the 3G shutdown. This effectively means that any device being used on AT&T’s network must be pre-approved. Unfortunately, even devices that are fully compatible with AT&T’s LTE network are being shut out because they aren’t on that list.

Customers across the web are complaining about their fully functional devices being shut out or having difficulties due to the whitelist. AT&T is automatically suspending people’s lines if the device on that line isn’t on the allowlist. //

Verizon and T-Mobile are also sunsetting their 3G networks. They, however, are not using such a strict allowlist system. Both carriers simply require devices to be compatible with their respective Voice over LTE technology, which most devices do. AT&T seems to be the only carrier that is actively rejecting compatible devices. //

https://www.xda-developers.com/will-my-phone-work-on-att-after-3g-shutdown/