I just wanted to share my experience with changing my departing flight with AA:
Firstly, I was emailed about two weeks ago that my departing flight for later this year was to leave at 20.05 instead of 17.40...which meant arriving close to midnight and too late to do anything!
So I contacted the 1300 number and successfully changed my flight to an earlier one the same day for no charge.
If AA change a flight by more than 2 hours, then you can apply for a credit or change to another flight on the same day (if available).
Yes it took a few attempts to get through on the number, but when I did, I was pleasantly surprised that I managed to change our flight.
Took about 10 minutes on hold and all done and able to get aisle seat and row 9 (was originally in row 6).
So I am happy with their service and that I could change the flight to enjoy a dinner in Bali on our first night!