If it's still within 30 days of the delivery date start a return on here:
https://www.ebay.co.uk/help/buying/returns-refunds/return-item-refund?id=4041
select "Item doesn't match description" and escalate it to eBay after 3 complete working days.
If it's more than 30 days it's too late to do anything via ebay but contact your payment provider and ask about a refund or chargeback.
If you want to speak to someone at customer service we have no direct link now so click on the help link at the top of any page. Select a topic then scroll down to Contact Us. Get to automated assistant and put in the question box Can I speak to an agent?
