There are two ways to get refunds:
1. Submit a Refund Request online at https://www.endicia.com/Account/Tools/PostageRefund/ (you have to log into your account first)
When processing these refunds you will need to enter your Endicia website log in details. These are different to the credentials which have been entered to the Endicia shipping extension through Magento.
For instructions on how to process a refund via this method, then please follow this external link:
http://www.endicia.com/printablepostagehelp/content/general/refunds_request.htm
2. Enable Endicia Auto Refund Service at https://www.endicia.com/Account/UpdateProfile/AutoRefundService/AutoRefundService.cfm (again, log in first) which will automatically refund the label if it hasn’t been used within 30 days of creation. This is a nominal charge each time a label is auto-refunded. After this you can still submit refund requests for free, but if you forget to refund something it’ll automatically be refunded (less the nominal charge).
Please follow this link on details for this process:
http://www.endicia.com/landing-pages/auto-refund-service