You need to utilize the eBay returns by clicking RETURN THIS ITEM in the drop down menu next to the item in your purchase history. eBay will only get involved if you follow procedures.
Assuming you are the buyer read the link below it will give you steps on how to return. You have 30 days from date of delivery to open a return through eBays Money Back Guarantee.
Sellers should already know how this works.
Returns, Items Not Received, and Refunds for Buyers
