AT&T

AT&T Inc. is an American multinational telecommunications holding company headquartered at Whitacre Tower in Downtown Dallas, Texas. It is the world's third-largest telecommunications company by revenue and the largest provider of mobile telephone services in the U.S. As of 2023, AT&T was ranked 13th on the Fortune 500 rankings of the largest United States corporations, with revenues of $120.7 billion.During most of the 20th century, AT&T had a monopoly on phone service in the United States.