I have experienced similar things in the past week, all with the same AA agent, who is actually very nice, and I don't want to mention his/her name.
Did you try calling back at a different time, such as M-F 9-5 DFW time?
Then a couple of days ago, I made changes to a separate DONE4, this one did not involve any CX flights, only AA and QF. They were only date and time changes, but again I have been told (coincidently, by the same ticket agent) that I will have to go an AA ticket counter to have the ticket reissued.
Is this a paper or E ticket?