If you'd like to delete an instance, and free up it's slot for reuse, you can do that on the instances tab on the control panel.
There is no way to undo or cancel a deletion. We will delete all backups stored for both the live and UAT/Staging copy of the instance, right after you request it. Make sure you've downloaded a backup *first*, and make sure you're deleting the right instance.
There is no going back once this process is started!
Login to the panel, and select the instance that you'd like to delete. Then, from the 'Settings' button, click the 'Delete' option at the very bottom;
The system will ask you to confirm. Enter your password, click "I am sure", and the instance will be deleted.