Disable Caller ID blocking on AT&T U-verse Voice by logging into the user's My AT&T account online, selecting Voice Features under U-verse Voice and selecting Caller ID Blocking in the Outgoing Calls tab. From there, select Off, and save the changes.
Individual mobile phones and smartphones have different features and settings when it comes to unblocking a call, as of 2015. For example, to unblock calls on a Samsung Galaxy S4 powered by AT&T, press the Menu key from the home screen, followed by Call Settings. When the Auto-Reject List appears, select individual phone numbers to drag into the trash can. Doing this takes each individual number off the blocked list.