Nope.
No refund, no change to feedback.
If you change the feedback now, from someone who was adamant about refunding before, the chances of getting one after your remove your only tool are small.
That being said, since there was a problem and the seller was uncooperative, why did you not open a Dispute before leaving feedback?
I quite understand if you did and were instructed to ship the unwanted item overseas using Confirmation of Delivery. This is generally too expensive for the kind of item purchased overseas.
Disputes do a much better job of putting bad sellers on eBay's radar and possibly getting them kicked off the site than feedback.
The other overlooked tool is the Detail Seller Rating system. When you leave feedback you are also asked to Rate the seller in four categories. A normal pleasant transaction gets Five Stars. The lowest Rating is ONE Star. No stars is a free pass.