What a mix up!
Getting a MAC isn't the right way to go, since a MAC key transfers a service to another ISP, and in effect you'd simply be transferring the other persons adsl.. and sure as heck AOL wont help with that one.
BT Wholesale wont help because they will only speak with ISPs, However there is a special department which is was specifically set up to deal with MAC issues Tel: 0800 169 0934
I would have thought that the ISP you wish to go with is the one who should be chasing this for you, but it would need to be an ISP who understands the system and one who is able to take this up with BT Wholesale on your behalf.
I'm away for a couple of days now, but theres a few ISP reps that read this forum, so maybe one of them could comment what the proceedure would be and if they can help.