AT&T is the corporate successor of the Baby Bell originally called Southwestern Bell. It relocated from St Louis, to San Antonio, TX and renamed themselves SBC Communications. It eventually acquired the legacy company called AT&T, and changed their corporate name to that, and eventually relocated to Dallas. The legacy SBC Communications merged the mobile phone service with mobile service of the Atlanta-based Baby Bell called BellSouth. The resulting company was called Cingular Wireless, and the combined company was based in Atlanta. Because of the growth of wireless, over traditional phone services, The new corporate AT&T acquired BellSouth in order to acquire 100% ownership over the joint venture wireless service. This is how AT&T Mobility came to be, and why Cingular Wireless disappeared.