AT&T Inc. is an American multinational telecommunications conglomerate, headquartered at Whitacre Tower in downtown Dallas, Texas. AT&T is the world's largest telecommunications company. 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; combined with AT&T's legacy U-verse service, this also makes AT&T the largest pay television operator. AT&T is the second-largest company in Texas, behind ExxonMobil. , AT&T is the 12th largest company in the world (non-oil and overall) as measured by a composite of revenues, profits, assets and market valuation. AT&T is the largest telecommunications company in the world by revenue. , it is also the 18th-largest mobile telecom operator in the world, with 134 million mobile customers. AT&T was ranked at #4 on the 2017 rankings of the world's most valuable brands published by Brand Finance.