this note on Sony’s XA2 page
AT&T announced that it is phasing out its 3G network to make room for newer technologies to improve the user experience. As a result of this change, certain Sony® Xperia® phones will not work on the upgraded AT&T network after February 2022.
We are working closely with AT&T to minimize disruption for our customers. Sony is working on solutions to help keep Sony customers on the AT&T network. This page will be updated with additional details in the near future. Please bookmark this page and check back periodically.