Sounds as if both the passenger and the agent were having bad days. If you're entitled to cancel the ticket due to the aircraft swap, is AA now saying that they won't do this because they consider you or your child a threat? I'd think they'd be fine with cancelling your ticket in this case. Regardless, will you be at an AA-served airport anytime in the near future so that you can speak to an agent there to cancel and refund your ticket? Or, try calling again to get a more more sympathetic agent to refund/change your ticket?