As of 2015, AT&T does not offer its own reverse number lookup service, but rather refers their customer to the service that is provided on Yellowpages.com. This advice is prefaced with a disclaimer that any information found using the service is not provided by AT&T, but by a third party.
Consumers can use the reverse lookup service by visiting the Find a Person page on Yellowpages.com and using the phone number option. Once they click on this link, users are prompted to enter a 10 digit phone number with the area code included. Searches that do not yield results lead to an offer for a paid service from Intellius.