We got a refund from Delta on a "non refundable" rate last year. The company had changed our flight schedule a bunch of times. Finally,I called customer service and the rep grumbled but I recieved a 100% refund. The rep did say that they get lots of requests for refunds because of all the schedule changes.
Also,on the foreign customer service reps,an American Express agent told me that I could request an American agent at anytime. I don't know if this is true with all companies but it wouldn't hurt to ask. Before the flames, I have no problem with foreigners. It's just much easier for me to clear up refund disputes with someone I understand a little bit better.