AT&T Messages Backup & Sync stores your text and picture messages in the AT&T cloud and syncs them to your supported smartphone. Note: You can also, access your messages and send or receive messages using your mobile number from your tablet or computer at messages.att.net.
To turn AT&T Messages Backup & Sync on or Sync Messages, from the home screen, tap the Messages icon.
From the Messaging inbox, tap the Menu icon.
Tap Settings.
Scroll to and tap AT&T Messages Backup & Sync.
If AT&T Messages Backup & Sync is not enabled, tap Turn it on.
Tap OK.
If AT&T Messages Backup & Sync is enabled, tap Sync Messages.
To cancel the service tap Stop Backup. Note: You can also log into att.com/myatt or the myAT&T app and remove AT&T Messages Backup & Sync from the mobile number that has the service.