To cancel a label, go to My eBay > Sell > Postage Labels.
You'll then see a list of all of your active postage labels.
Next to the label you want to cancel, click 'More Actions' and then click 'Cancel Postage Label'.
You only have a few days to cancel your postage label for a refund. After that deadline, I'm not sure how you would go about getting a refund.
All the best.
