I tried and failed. The problem is that they will need to reissue against the new rules/rates. Now that is not too much of a problem if you want to change a ticket for which the price has not risen. In my case (bought the ticket 10 months ago) it would mean an additional ZAR3500,-.
The $125,- fee is not required if the flight is only a date/carrier change.
AA has more problems than Amadeus based carriers like BA. CX has issues too and I do not know about JAL.
Mind you: I am just basing this on my own experience. Not an expert.
The AA systems have problems with D/AONEx's anyways. A lot of people cannot retrieve their itinerary online.