If you do make a reservation and have to cancel, be sure and keep those numbers.

I checked my CC bill online today and saw a charge for a hotel I'd CXL'd last month.

Dug thru my stuff, called the hotel and told them I have a cxl #. They are now crediting my account !

Good advice! I always print out all reservations and cancellations and keep them at least till I check the CC bill. Never had a problem with cancelations, but once had a problem with a hotel overcharge, good it was at check-out, I produced my print-out with a different rate, and the clerk changed the charge immediately. I still kept this print-out till I got my CC bill later - just in case.

Good idea, since I had the experience of checking out of a hotel, and the girl typed in the wrong amount on the CC machine....then she canceled it, and put in the correct numbers. She said ' oh don't worry, I canceled it in time, you won't get charged twice.' But when I got my bill....I had been charged twice.

Luckily, it was easily straightened out, since I kept all the checkout paperwork.

Good advice! This happened to us just recently when we spent the weekend in Philadelphia. We had booked a hotel about a month in advance, but found a better one. Canceled that about 2 weeks in advance. Got a cancellation number.
Not only did we get billed but we got billed MORE than the room was quoted to us!
After two phone calls to this hotel, they kept saying they would take it off, but every time we looked at AMEX online, it was still there, we had to call AMEX to have it taken care of.
AMEX did it easily and quickly but did ask for that number.

Better yet, if you can tell the hotel the name of the person who cancelled your reservation, along with the cancellation #, that will blow their minds! I try to jot down the name and number of people I talk to on important matters. They think you are just trying to be personal when you call them by name, but I'm really verifying it while I'm writing it down. This has helped with cancelled appointments, instructions, etc. I keep my records after check-out, too. Just in case the hotel pulls a fast one. And you should scrutinize your ATM/Debit Card charges with your bank. Once I got charged twice for the same amount and the transactions were a few days apart. Since the dollar amount was an odd number, the bank took it off immediately and then verified the transaction information. We still can't figure out what computer glitch caused that error!