The only way for you to get your final value fees back is to offer the buyer a mutual cancelation request. If the buyer agrees to the request or doesn't respond to the request, you get your fees back. If the buyer refuses the request, you won't get your final value fees back.
Here is how the process works.
You should make the request while the PayPal case is still active, if the dispute closes before you make the request, you won't be able to make the request as only one case per transaction is allowed.
