What to do if an eBay seller doesn't communicate with you?

Ok here’s what happened: I won this auction on eBay for a rare cell phone. Before the auction ended, I asked the seller a question and he never replied. But since it looked like such a good deal, i still bid on it. After I won the auction, I contacted the seller again and he still has not replied. I still have not paid him yet. I have a feeling that the seller is a scammer since when I looked him up i found another account with a similar username (the last digit was different) with really negative feedback. So how long should I wait before reporting? Also since I am not paying, can he report me on eBay for not paying? Is there a way to cancel this transaction?