Originally Posted by anabolism

AA is very fond of recalculating taxes and airline-imposed fees whenever making a voluntary change. Since this is an xONEx ticket, you might try asking a different OneWorld airline if they would take over the ticket and make the change. You could ask CX, for example. If they quote you an additional add/collect that's the same or more than what AA quoted you, just thank them and hang up.

The ticket would need to be reissued, but the $125 fee would not apply. That fee is for route changes. Certainly AA would not charge the $125 fee for making date/time/carrier changes only.