He said item has problem，not work，we gave him suggestions for him to try，he said still not work，he want to return it back. We
said he can return it back for refund, he said he don't accept paying return shipping fee,we said OK,we can send him a return label,so he don't need to pay return shipping.
But he said he just want to open case on us to let ebay step in.
We already gave everything he want,but he still want to hurt our business on purpose.
Since the item did have problem,so ebay would properly stand on his side,and won't help us.

So suggestion for all seller, block this buyer,so he won't able to buy from you. If you let him buy from you, any problem happens,that would be waste your time to help him,he will hurt your business anyway by open case on you no matter how nice you do your job.