Refunding a Buyer--full item not returned

[trolley_trove]

I'm still in my rookie year of selling on eBay and haven't dealt with many returns.

I sold a group series of DVDs and the buyer wanted to return them because they weren't playing on their system. The return was approved due to them not working.

I received the item back today; however, they only sent one of the DVD's series back instead of all three. What should I do? Just refund the whole purchase or can I refund part of it? 

[donsdetour]

You can offer a partial refund giving the reason you stated (they may or may not accept)

but:

eBay will see that you have received item returned: and refund them for all.

 You can also file a report with law enforcement for theft as well if you have to give full refund.