Can I get fee credit on a partial refund on an item

[flyingpigs]

Pls read details.

A buyer decided they didn't want a item I sold them but claimed it was broken on the returns form, on return there was nothing wrong with it and after a long string of messages they seemed to accept they were caught lying. However, I found out that eBay does not allow me or the buyer to change the reason for return without opening up a case. It seemed like a lot of hassle, so I did a partial refund, which was the item cost minus delievery. But now I've found out that eBay only provides fee credit on full refunds, or at least that is how it is written, and my invoice shows them charging me for the item that was returned.

So my full question is, can I open a case to get my fee credit or am I simply buggered by the person who decided to lie about their reason for returning?