On AT&T's network, primary service lines are often given special perks. For some customers, AT&T even offers "early upgrades" on the primary line. On Unlimited Talk family plans, the primary line also gets unlimited calling without having to pay the much higher costs required of a secondary line. Switching one of the phone numbers to the primary line, for any reason, is extremely easy, and takes little time to do.
Changing the Primary Line
Contact AT&T's customer service department. This can be done by dialing 611 from any wireless phone on the account, or by dialing 1-800-331-0500 from any other phone.
Follow the prompts over the phone to speak to a customer service representative.
Hand the phone to the primary account holder. The customer service representative will ask for the account information and to verify their identity before the account can be accessed.
Request that the customer service representative change the primary number on the account to the new preferred one. The representative will easily be able to make the change, provided the primary account holder verifies their wish to change it as well.