What do i do if buyer doesn't want to return item on ebay?

So a buyer purchased an iphone 3gs from me and he was dissatisfied at first he wanted a partial refund but i told him that i can't do that and that i could only do a full refund if he returned the item, so i agreed to give him a full refund when the item is delivered to me but know he said he didn't want a full refund he wanted a partial one so he decided that he wants to keep the item and he gave me bad feedback, but the case is still open how do i close the case if he doesn't want to return the item anymore?

Added (1). Yes but how do i close the case? The buyer opened it!

Just close it.

The way you solve this is, go into the feedback he gave you and insert your explanation
as you have done here, in as few words as you can manage.
This is so that future buyers can read the problem your buyer gave you and how you resolved it.
You did everything just right. He was trying to scam you into getting half of the money back.
Do this, and all will be solved.

If he has entered into the dispute that he does not wish to return the handset, then
add your response "Buyer has indicated he does not wish to return item"
ask ebay/paypal to close it.

Add calm, factual followup to feedback, stating "Buyer was offer full refund upon return of handset"

You have to contact ebay support to see if they can close it from their end.