AT&T urges customers to buy new phones to keep using its network
The email obtained by AndroidPolice and published on AT&T's official forums is quite vocal and “demands” people who own certain phones to buy new ones that are compatible with the carrier's network as quickly as possible.
In fact, even some phones that feature 4G data and calling support like the Samsung Galaxy S10e and Nokia 6.1 won't work on AT&T's network effective February 2022. The main issue with the email is the way AT&T chose to communicate this in total disregard with the times we're living, and how it presents it as a “do or die” situation even though we're still more than a year and a half away from the deadline.
AT&T has already published a list of smartphones that are compatible with its 4G data and calling services, so if your phone is not there, chances are that you'll get such an email pressuring you into buying a new phone in the next 19 months or so.