Southwestern Bell - became AT&T inc by buying Ameritech, AT&T Corp. Pacific Telesis, BellSouth (all Baby Bells)
Bell Atlantic/NYNEX - merged to become Verizon buying GTE, MCI Worldcom along the way
US West - merged with Qwest, acquired and became CenturyLink
"the original AT&T" is those Baby Bells not just the empty shell that became AT&T Corp. (aka ATT Long Distance)
The takeaway is that the ORIGINAL AT&T split into 3 companies and swallowed GTE, MCI, Worldcom, and Qwest in the process. It ended up being a consolidation. 4 of the 7 baby bells are back together operating under the AT&T name, that's over half the old company.
Consolidation started with Cingular buying AT&T Wireless. Then SBC bought AT&T and simply kept the AT&T brand. Eventually the Cingular brand went away and they went back to AT&T and AT&T Wireless.
Wheeeee! The AT&T of today is basically SBC with all the old assets rolled in. SBC bought AT&T, not the other way around.
Source: worked there through it all