D700 eBay PayPal dispute

Hi

I just sold a d700 on eBay all fully working and packed very carefully to send off.

The user received the item and 6 days later sent me a message on eBay asking for a return saying it doesn't autofocus like a d700 and he wants to get a d800 instead.

I refused the claim stating that a d700 works like a d700 and that eBay is not a shop where you can buy something try it for a bit and send it back.

He's now opened a PayPal dispute and PayPal have frozen the money from my account.

He has raised the claim stating internal damage.

Now if there was damage in transit this would of been fairly evidential.

I have photos before taken with the camera and I know it works.

Has anyone else experienced this before?!

I Can see from his eBay that he has since bought 2 new lens so he is either new to Nikon or maybe photography all together.

Thanks