not sure if i understand this TA issue

1. the TA who issued your ticket can do the changes (and should). he will deal with the airline for rate approval/etc.
(this is what the commission is for)

2. the airline (in fact, all OW airline, not just BA) should be able to (and is obliged to) do the changes.

it should be your choice of who you would go to. the case is basically no different from when when bought a full far Y/J/F ticket from a TA and ask the airline to reissue.

but i think you will save time by asking the TA to do it. (waste his time, he is making 5-7% of your fare)

[This message has been edited by pegasus8228 (edited 11-13-2002).]