The seller still needs to pay the cost of the "return postage " The seller sent the wrong size dress?
Can someone send me a link to ask eBay to step in? As I am unable to do that on the dress as I have already received a full refund? Original postage and the price of dress?
There is no facility to get a refund on return postage after the event.
You should have opened a return case and the seller would have given you a returns label, if they didn't ebay would have issued one at the sellers expense.