This explains clearly what happened with AT&T, and its multiple acquisitions over the years:

http://videosift.com/video/Colbert-regarding-the-new-ATT

There's a lot more to it than the wireless piece. Today's AT&T was Southwestern Bell/SBC which as you said, acquired AT&T and switched names.

Thanks, didn't know.

Actually that is the company now known as AT&T Wireless. The company now known as AT&T was one of the 24 'Baby Bells' that were created when antitrust regulators broke up AT&T (the one that created Bell Labs) in 1984.

The company used to be known as SBC Communications but changed it's name to AT&T after acquiring what was left of AT&T (mostly long-distance phone services) in 2005.

Through a long series of acquisitions AT&T now owns 11/24 Baby Bells.

Sources:

[1]http://en.wikipedia.org/wiki/AT%26T#History

[2]My grandfather worked for AT&T for his entire career and I've involuntarily listened to a minimum of 100 hours of company history throughout my life.