Mine waived the fee for the next session once when he had to suddenly cancel for a reason other than being sick.

We were once in a bit of a dispute and had to hammer it out. I paid for one session of dealing with it and then we had an extended phone call about it, which I didn't get charged for. I thought that was fair that I didn't pay for the entire process of dealing with it, as we both were responsible for what was going on.