We ended up pulling the SIM from the iPhone and putting it into the ADP1(what acronymn should I be using?). He changed my account from the iPhone plan to the PDA plan ($10 more/mo). I forgot at first that I have to hit MENU during setup to configure it for AT&T -- so once it failed, I did that...
I have 4 different set of APN settings, and the rep didn't know wha the correct settings were. Everything worked except for MMS and I spent all night trying to get the MMS working. Finally, this morning I called customer service.
So ignoring for a moment that a previous tech support rep (myself) forgot to try rebooting after changing the settings -- there was actually something that had to be done on their end. Specifically, they were unable to change the IMEI on my account and it kept insisting I had an iPhone. Their tech support department was fairly sure their side would prevent MMS as long as it thought I had an iPhone (even though the account block for MMS was removed).
Finally, they had to manually remove the iPhone from the account and then enter my IMEI separately. It showed up as 'ubertracker' and they removed that so that it showed as 'unknown'. Reboot again and it started working....
In case anyone is looking for the settings:
MMS Proxy: wireless.cingular.com
MMS Port: 80
** THEN SAVE AND REBOOT **