Recently I am in love with using USPS'S CLICK-N-SHIP service, especially during holiday season,
avoiding the long line, and avoid to meet any unhappy USPS worker.
It happened few times while I use "CLICK-N-SHIP", sometime it charge me twice. Today, I learned how to get refund.
See there's a Request Refund buttom? That's it, after click on that, I believe you know how to finish get your refund back, good luck.