You cannot report this to eBay as they do not offer warranties or guarantees on items, just that they are just as described on receipt. If they are not, a buyer has 30 days under eBay's 30 day MBG, Money Back Guarantee policy, to return the item for a full refund.
If you bought this from a Private seller you are too late to claim a refund. You could try your payment provider but not quite sure if they can help you here.
If purchased from a registered UK business, who offered a guarantee and is now not upholding this, then turn to Citizens Advice for your next steps, if you wish to take this further. Obviously depends on the cost of the shoes, whether it's worth your time to pursue this way.
