Cingular was formed in 2000 by the joint venture of SBC Mobility and BellSouth Mobility. It has its roots in BOTH SBC (or Southwestern Bell), and BellSouth, as well as having taken over licenses of other cellcos over the years, such as much of the "old" AT&T Wireless.
The year-2000 arrangement was that SBC owned 60% of Cingular Wireless and BellSouth owned 40%. The HQ were in Atlanta, which was also the HQ of BellSouth.
SBC, which dates back to Southwestern Bell, but had also bought out Pacific Telesis (California's Pacific Bell and Nevada Bell), Ameritech in the Midwest, and SNET of Connecticut ... bought out its pre-1984 parent company, AT&T, the one-time parent company of the entire Bell System, and changed its own name to "lower case" at&t, as well as changing AT&T Long Distance to "lower case" at&t. This all took effect in late 2005 officially, and began to become publicly visable with early 2006.
Effective with the beginning of 2007, SBC's at&t finally buys out BellSouth, after getting the go-ahead from both federal regulatory agencies and the regulatory entities of numerous states. This now means that Cingular Wireless is 100% owned by SBC's at&t, and as such, even the Cingular name is being changed "back", but now to "lower case", at&t.
_________________________________________________________________ Now you can see trouble before he arrives.