I just had a recent experience that made me curious about the airline's responsibility to disclose its $5 telephone/res agent service fee.

I called to apply the value of a canceled ticket to a new reservation that I had made. Never in the course of the conversation was I told about a $5 fee for helping with this, though I assumed it was going to charged.

Lo and behold, I was not surprised to see the fee on my AmEx statement. Does the airline have a responsibility to inform that they are charging you a fee and provide a receipt for the transaction? They should train their agents to be more consistent in telling people about it.