If the buyer opened a case for item not as described, then there is no option to refuse it. You need to accept the case and refund within 3 days, or pay for the return postage if you want the item back first, then you have 48 hours to refund. Stick within these time lines, and your seller performance will not be affected.
You can then appeal the decision for the refund. I won't admit it's easy, eBay do not see the item, and they do tend to fall on the side of the buyer.
This is the process:
https://www.ebay.co.uk/help/selling/managing-returns-refunds/appeal-outcome-case-seller?id=4369
@davy-jeff
