Do ya think I can get out of paying this?

So, I'm kinda ticked at Wyndham hotels right now. That's where the Stargate convention is. So, each year I've booked a room using their "web exclusive" rates, meaning the room cannot be canceled and your credit card is charged immediately, as opposed to after the stay. I booked the room on June 9th. Received e-mail with the confirmation information and another note on there that the credit card will be charged THAT SAME DAY. Now, here's where it may fall apart slightly. We didn't really look over the credit card statement for the next month to notice that I had not actually been charged. No, that surprise came when we get the next month and it's about $500 higher than we were expecting. Why? Wyndham didn't charge me until after we'd completed out stay. Now to me, that is a violation of the terms and conditions that I had agreed to upon booking the room. Why should I have to pay for their fuck up? Right? :-)