Do you have status? Have you asked for a change fee waiver before?
Something tells me AA is not generous with change fee waivers. Especially when you were hidden city-ing to get a discount.
What reason would you give them to ask for a waiver of the change fee? What is the change fee on your ticket?
Maybe they will give you 50% off the change fee if you ask nicely and haven't had a discount/waiver before...