Personally, I would take the package to the Post Office and buy a new label there.
You can cancel the label you bought from Ebay - see below - but it will take a few days to get your money back.
How to cancel a postage label
Labels purchased on the eBay labels platform need to be used within 14 calendar days. If unused, make sure to void the label within 14 calendar days to get a refund.
Here's how to void a postage label in My eBay or Seller Hub:
- Select Selling in My eBay, or select Orders on the Seller Hub Overview page.
- Select Postage Labels on the left-hand side.
- Select Actions next to the label you'd like to void, and select Void Label
"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)