When I have done a house clutter purge I will donate some things to charity or sell the items on Ebay. I'm not going to get into how to use Ebay, but tell you about my experiences with their complaint service.
If you have a problem with an Ebay vendor or buyer and you can't negotiate on your own with them, then use the complaint service that Ebay provides. I have had very good luck with them with a couple of purchases that didn't work out.
First of all, make sure that you get your product in a timely manner and in good shape. Check closely to ensure that you have actually gotten the product you ordered and not a cheap substitution. When a vendor says that it's not their responsibility, don't believe it.
Provide the complaint service with as many facts as possible in the order they happened. The more info you give them the better they will be able to investigate.
Here are two scenarios that happened to me:
I had purchased gold jewelry findings from a vendor, but they never arrived. I had paid for priority mail, so that they would come quickly and to provide tracking. When I contacted the vendor he claimed that the package was mailed, but he wouldn't provide me with the postal tracking number. I had a feeling that the package was never mailed and if it was, it was not sent priority mail. Ebay told him to provide a tracking number, it proved to be a false number, so Ebay took the cost and postage from his account and credited my account.
In the second transaction I had ordered a Speedo brand, lycra fabric. When I opened the package the pattern on the fabric wasn't right. I checked the selvage of the fabric and saw that it was a different brand completely. The vendor told me to return the fabric, but that I had to pay the return postage. Ebay said differently, I was credited with the full amount and the vendor decided to let me keep the fabric rather than pay return postage.
I strongly recommend that you take advantage of Ebay's service rather than ignoring a disappointing transaction. You might be pleasantly surprised at the outcome.