Starting February 22, 2022, AT&T will begin phasing out it's 3G/HSPA wireless network service in the USA (including Puerto Rico and the US Virgin Islands).
If your device (phone or other devices) do not have the capability to use the 4G that AT&T will be using then you will need a new device or a new provider.

This will not affect Canadians unless they are using the roaming feature to phone a USA number.

The shutdowns will only impact mobile devices that do not support 4G LTE data and Voice over Long-Term Evolution (VoLTE) roaming.
The devices effected will not be able to make or receive wireless calls (including a 911 call). Send or receive messages or use cellular data while roaming in the USA.