☎ 1-888-720-8856 AT&T mail Customer Care Number . AT&T is the largest telecommunications company in the world by revenue. As of 2016, it is also the 17th-largest mobile telecom operator in the world, with 130.4 million mobile customers. AT&T was ranked at #6 on the 2015 rankings of the world's most valuable brands published by Millward Brown Optimor.☎ 1-888-720-8856 AT&T mail Customer Care Number . AT&T is the largest telecommunications company in the world by revenue. As of 2016, it is also the 17th-largest mobile telecom operator in the world, with 130.4 million mobile
