AT&T Inc. is an American multinational conglomerate holding company headquartered at Whitacre Tower in Downtown Dallas, Texas. It is the world's largest telecommunications company, the second largest provider of mobile telephone services, and the largest provider of fixed telephone services in the United States. The company operates through four segments: Business Solutions, Entertainment Group, Consumer Mobility, and International. The company was formerly known as SBC Communications Inc. and changed its name to AT&T Inc.