Whether it'll do you any good, the AA ATW desk phone number is +1 800 247 3247

If you were both waitlisted, then I assume that he was waitlisted 1st and so cleared when a seat became available.

Which airline did you make the change with? If it was QF/BA , QF require to sight the ticket to verify that the ticket is valid to be changed and they charge $25 for the privilege of doing it. If you had made the change with AA, then there would have been no such issue since QF wouldn't care since AA had taken the risk on the ticket validity

Dave