Cingular owns AT&T wireless, which was completely spun off from AT&T a number of years before they merged. I don't believe the two are related in any other way.. could be wrong.
You are correct that ATT wireless was spun off from ATT, but now ATT is owned by SBC (now SBC changed their name to ATT). ATT/SBC owns 60% of Cingular, the other 40% is owned by Bellsouth. (until ATT/SBC buys them too)
