Amid an economy-crushing pandemic, AT&T has decided that now is the best time to send a scaremongering email to some customers, telling them that their device "is not compatible with the new network and you need to replace it to continue receiving service." The email conveniently doesn't even explicitly mention that this will only affect customers as late as February 2022, only linking to that information.
https://www.androidpolice.com/2020/07/22/att-tells-customers-to-change-their-phones-or-they-wont-work-anymore/