You can remove a user through our admin portal. There, you go to Users > Account and login. Then you select the user you wish to remove, and select Delete on the right-hand side of the page.
The system will now ask you to confirm your selection and let you decide if you want to cancel the license. If the license has a bound time, then it will be reserved for use later on. The same goes for the numbers that were active on the user that has been deleted – they will stay at your disposal for when you add new users in the future.