I do think you can dispute the charge even after it's shown up on your bill, and been paid, but I think there's a relatively short window to do so (60 or 90 days). I'd call the card company ASAP and at least give them a heads up that there's a problem and you're trying to work through it with the guy.

Good luck - it sucks to wait so long for something and then not have it be right. We went through the same with our bike fridays - the difference is that the company was horrified, and has since made it right!

*hugs*

Carrie Anne