Go to the item on your selling page and click the dropdown on the right. Then select the option that refers to a dispute or case (I can't remember the correct terminology and I don't have any unpaid items at the moment to check. It could be something like resolve a problem). Don't select the cancel transaction option.
On the next screen you will be given some options. Select the one that mentions you selling an item and the buyer hasn't paid. Click next, or submit, or whatever it says. The next screen is where you'll submit it. The unpaid case is now open. If you go back to your selling page and refresh the page, you'll see a note under the transaction saying there is an unpaid item dispute open.
4 days later (and not a second before), go back to the item on your selling page and click the dropdown. Then select close case. The next screen will show a link to the transaction with a dropdown on the right. Click the dropdown and then click get fee credit. If on the next screen the option to select no isn't available, check the message at the top of the screen for the earliest time you can close the disput and go back then and close it. Once it's closed, you are free to relist.
