Have a look in your Purchase History to see if 2 items have been purchased if so, send the seller a message to cancel one order, be aware, they are not obliged to do so.
If you cannot see any purchases, in your eBay account, perhaps it wasn't used, and did you made the first purchase as a ' Guest Order' ? See here how to receive your order details for the item, and if necessary later, how to make a case for a refund.
https://www.ebay.co.uk/help/buying/returns-refunds/returning-item/returning-items-bought-guest?id=40...
@franciswayyy