Not sure why it (I'm assuming the Etsy app) is trying to buy two labels. I've done so accidently from time to time and you can get refunded for the unused label.
I'd start by going really slowly through the label purchase process and see if I could find where the app and/or I was ending up buying or being prompted for the 2nd label. And if I really didn't believe it was me I'd make sure my browser was up to date, reboot my computer ... the stuff I do when an app starts acting buggy. You can try to get Etsy's help but they'll want the details so the first steps will prepare for a chat with Etsy support.
Good luck.
