You really can't Force the person to sell you the 
cel through Ebay, you have to take it into your 
own hands

Its on Ebay's Rules...Check it out at

http://pages.ebay.com/help/community/notabuse.html

The seller refuses to answer my emails, they will 
not acknowledge my winning bid, or they have 
already sold the item. 

eBay cannot force a seller to honor their 
auctions. You should of course, leave appropriate 
feedback for the reluctant seller to warn other 
bidders of his or her past history. Depending on 
your local jurisdiction, you may have independant 
legal recourse against the seller.