kaled - 12:55 pm on Jun 13, 2010 (gmt 0)
I'm guessing but I suspect you'll have to live with this mistake. By all means, email their support service (be polite, use a sensible excuse and promise to use them in the future). You might get lucky, but if not then I think you'll have to chalk it up to experience.
Also, I think most people here would agree that registering a domain name as part of a hosting package is a bad idea - there are many horror stories out there.