T-Mobile cutting support for pre-VoLTE devices in 2021, AT&T in 2022

T-Mobile will stop supporting phones that aren't compatible with Voice over LTE in early 2021, with AT&T to follow suit in 2022.

Credit: AppleCredit: Apple
Voice over LTE (VoLTE) routes voice calls over a 4G LTE connection, instead of 3G. It's a standard, with many carriers requiring phones to have VoLTE before activating them. Apple's iPhone 6 and later support VoLTE.