He can claim all he likes, but unless you both mutually agree not to conclude the sale he won't get his sales fee back. Report him to Ebay and force the issue......pay for it...
In my experience leaving someone negative feedback rarely results in the same in return. If he/she doesn't complete the sale, as they are obliged to do, under Ebay rules, then you are completely in the right to leave them that neg feedback. And they in return are not.
Girf