It’s different.

There are currently four major mobile operators in the United States, from largest to smallest: Verizon Wireless (acquired Alltel), AT&T Wireless, Sprint Nextel (acquired Nextel), and T-Mobile USA.

The two major fixed-line operators in the United States are, rumored to be merged into CenturyLink, in descending order: CenturyTel (acquired Embarq) and Qwest.

AT&T is the largest fixed-line telephone service provider and the second-largest mobile phone service provider in the United States. It also provides broadband and pay television services. It provides services to a total of 150 million households, of which 85.1 million are wireless users. Southwestern Bell was founded in 1983 as one of the independent companies established as a result of an antitrust lawsuit between the U.S. government and AT&T. In 1995, Southwestern Bell was renamed SBC Communications. In 2005, it acquired American Telephone and Telegraph and changed its name to AT&T. In addition, it inherited the trademark originally held by AT&T and the name on the New York Stock Exchange. Listing code T (meaning telephone).

Reference material: Baidu Encyclopedia AT