Qantas actually called me and asked me to pay extras AFTER I have TICKETED, because their agents allegedly mis-calculated the fare when I made the payment. So just watch out.

Back to original, topic about refund. Never... don't bother. I once bought the last remaining L-class inventory, only to find the very next day, they have added a new flight and showing N9.... I asked for difference of $70 back, only being told that's not possible.