In your My eBay under Manage Postage Labels you can cancel the labels yourself up to 5 days after printing the labels.

If it has been more than 5 days then you'll need to contact eBay to see whether you can apply for a refund. From the main menu click on Customer Support then the Contact eBay tab and follow the steps until you get either a phone number or email contact.

Why wouldn't you use the existing satchels? C&S now has new satchels and the (old) C&S satchels are used for the eBay postage labels.