Don't ask for a voucher! I had booked a non-refundable J ticket DCA-AMS for later this month. I changed the return and the flight was about $800 cheaper. I got a paper voucher in the mail. Still no e-vouchers, which in 2017 is ridiculous. Regardless, if your ticket is wholly unused, do as others stated ... put a flight on hold and then call AA to exchange it.