That isn't how you do it. This is not ebay we are members like you, we do not deal with cases, we can only give advice.
If you haven't opened a case , do so now. Item has to be returned using tracked mail and when shown as delivered or attempted delivery you get a full refund.
If not on day 9 you escalate to ebay to resolve. If you can't prove delivery to the seller's address as provided by ebay you are unlikely to get a refund.
