This is always such a difficult and frustrating issue.
I recently had a similar issue with a client cancelling an apt 40mins before she was due to arrive, her reason being 'ive got too much on and am too busy.' It was a 2.5hr slot on a friday and I had turned away so many people! I was furious. When I tried to call the client to ask if she would be re-booking she would not answer the phone, It states clearly on our price list a 50%cancellation fee may be incurred if 24hrs notice is not given.
In many cases a client offers to pay and realizes their causing you inconvenience, it is then down to you as an individual whether or not you decide to accept or honor their offer.
I have now introduced a deposit policy to the salon where a deposit will be taken to secure any booking over 1.5 hrs, it is deductible from the cost of the treatment and maybe non-refundable if 24hr notice is not given for any cancellation. The client gets to spread the cost of thier treatment and my time is covered....win win situation.:biggrin: