there should not be a fee.
this is rebooking, not re-routing.

however, AA seems to have their own interpretation. you should call BA to make the corresponding change.
if this does work, simply make a separate booking, tell them your ticket #, and booking class (A/D/M) when asked

(edited for errors)

[This message has been edited by pegasus8228 (edited 01-05-2002).]