Was it listed with Simple Delivery?
If it was, then the buyer paid Ebay for the label and that amount did not go through your account.
If you didn't pay for that label, and you use an alternative method of posting, you can't get a refund.
The buyer will be refunded the amount paid to Ebay if the label isn't used.
If you bought the label from Ebay, you can cancel it and get a refund.
"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)