Barb, reading your situation mentioned, I think that is why I have always preferred to correspond through e-mails, and I just save them all. I had someone change a price on me like that too, and I hadn't sent a deposit yet, so I just backed out of it. I always state my prices in the e-mails to buyers so that they can hang on to it and know that I won't try to rip them off.
I do ask for a non refundable deposit of half, but I did recently have someone run into a financial problem. I offered them a refund, because it wasn't anything that they had control over, so it wasn't fair to them. Things happen that are beyond our control, so if that's the case, i try to bend a little.