You did not buy anything from Ebay - they don't sell to buyers.
If you locate the email you received from Ebay when you paid for the item - in your private emails, rather than your Ebay mailbox - that will enable you to check all details and make absolutely sure that you did not buy as a guest or from a second account.
When did you make the purchase? You have 30 days from the latest estimated delivery date to open a claim.
"There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.”
Søren Kierkegaard, Danish philosopher (1813 - 1855)