During any time that your end-user can no longer use the service and you decide to terminate the license, you can remove a license used by that end-user. To do this, hover over to the left side menu and go to Manage > End User
Step 1 - Go to the left side menu and under "Manage", click on "End-User"
Step 2 - Choose the end-user that you wish to remove their license
You can search for the end-user by typing in their email in the search bar
Step 3 - Go to "Actions" and click on the three dots. A dropdown will appear
Step 4 - From the dropdown, choose "Remove End User"
Step 5 - Select the service you want to remove its licence
Step 6 - Make sure to click check on "Remove the quantity of the licences"
Step 7 - Click "Remove Selected"
You can't reduce the number of licences for your subscription if all licences are currently assigned to users. To reduce the number of licences, first unassign one or more licenses from users, then remove the licences from the subscription.