The Seller should have refunded you immediately on delivery of your unwanted purchase.
Go to the Dispute and enter the tracking number and state that the package was delivered on September the whatever.
If you do not get a refund from the seller by Monday, call Customer Service and ask them to step in.
EBay will refund you and go after the seller for their money. He will also get a Defect.
You could do this on Sunday, but you would probably be dealing with the overseas clerks , who have more limited authority. So go for the Utah staff next week.