It all depends when you bought them. If you are within 30 days of the item's last estimated date for delivery you can return them at the seller's expense for a full refund. eBay's 30 day MBG, Money Back Guarantee is written on the right hand side of all listings.
If this time has expired, you could try your payment provider.
Best to always check all items on receipt for authenticity and below is the link to explain how to claim and how eBay's MBG works:
https://pages.ebay.co.uk/ebay-money-back-guarantee/
@fau-9769