Ebay question???????

-Basically, im the seller and someone won the auction but the buyers changed his mind because i missed out a crucial piece of info about the item and we have agreed to call of the deal...... Im just wondering what I have to do on ebay to cancel the deal and avoid paying fees for something i havent sold?http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=250849260061&ssPageName=STRK:MESELX:IT#ht_500wt_978