AT&T was actually the one bought out years ago (2005 I think) by Southwestern bell(SBC), they bought out AT&T, then bought out bell south, which gave them 100% ownership of Cingular wireless. They decided to change the name to a more recognizable name AT&T since they owned the rights to it.
So the AT&T today has little to do with the original.
Yes, your exactly right. Here is a little timeline of the "new" AT&T
1984 - Southwestern Bell Communications is spun off
1987 - SBC acquires Metromedia Cellular, becomes 3rd largest cellular provider
1993 - Moves headquarters from St. Louis to San Antonio
1995 - Changes name to SBC Corporation
1996 - Acquires Pacific Telesys
1998 - Acquires SNET (Southern New England Telephone)
1998 - Merges with Ameritech
1999 - Purchase Comcast Cellular
2000 - Merges wireless into 50/50 joint venture with Bell South, wireless division becomes Cingular
2005 - Acquires AT&T Corporation
2005 - Changes name from SBC Corp. to AT&T Inc.
2006 - Merges with Bell South
2007 - Wireless division (now wholly owned) becomes AT&T Wireless
2008 - Headquarters move from San Antonio to Dallas
2008 - Purchases Dobson Cellular
2008 - Purchases Centennial Cellular
2013 - Purchases Leap Wireless
2015 - Acquires DirecTV