I was stupid and didn't double check my check-in dates when I booked on priceline.
When I caught it, I called the hotel (Sheraton Centre Toronto) to see if I could change it. I told them that I booked on priceline but put in the wrong dates. He tried changing it but told me that they were sold out on the nights I wanted.
A few minutes later, I tried calling again to see if I could get a credit or something, but I figured I'd trying asking for a date change again. A super nice young lady helped me out was able to change the date.
She gave me a confirmation number so hopefully I won't be out of a place to stay on my vacation in 2 weeks.
Moral of the story: keep trying if all seems lost.
Hope that helps.