Originally Posted by Often1

Almost certainly will no longer work with better internal controls in place. The $450 remains non-refundable. Thus, if you purchase a $600 ticket, you will pay $150 in new money and that will be refunded. The $450 will remain a credit, but on 5/22, will expire.

Originally Posted by kop84

4. will work sometimes. If the refunds department notices it is an exchanged ticket the original non-refundable amount would stay non refundable and you'd be refunded the amount you paid over the original $450.