AT&T 1-888-720-8856 AT&T Mail Helpline Number is an American multinational telecommunications conglomerate, headquartered at Whitacre Tower in downtown Dallas, Texas. AT&T is the second largest provider of mobile telephone services and the largest provider of fixed telephone services in the United States, and also provides broadband subscription television services through DirecTV. AT&T is the third-largest company in Texas. As of May 2014, AT&T is the 23rd-largest company in the world as measured by a composite of revenues, 1-888-720-8856 AT&T Mail Helpline Number prof