Sorry to disagree with most but yes, AA general reservations have instructions not to touch a RTW, so unless you happen to catch, by luck, an inexperienced agent who simply goes ahead with the change, without thinking, you are going to have to wait for the ATW desk.

So, IMO, the answer is yes, that's the way it is, but no, you don't have to take it... just keep on calling and chances are you will get an agent who will make the changes for you.