Thanks for your replies..

I called AA RTW again and initially was told the same ie I would have to pay the current fare (there was information that had been added to my file). However, I asked if a supervisor could call me to confirm this. Anyway, apparently the agent decided to check into the ticketing herself and called me back later to say that I had received the wrong information and that I could re-route my ticket (it wasn't the first segment) and I would just have to pay the $125 change fee plus taxes etc. She was very helpful.

So the moral of the story don't always except what you're told by agents and if you think something is wrong try again.