Respected sir/madam,
I recently booked and online trip via airfare.com. When a family tragedy occurred I had to change the date of my departure. As the ticket was non-cancellable and non-refundable I expected to pay a penalty for this action. I checked directly with the airlines (United and China Southern Airlines who were both wonderful to deal with) and they both said that an admin fee of $250 would take care of the problem. I felt that this was fair and was prepared to pay. The airlines recommended that we make the change through airfare.com since that was how we booked it.