Administrators can remove team members from all teams by designating them as “inactive”. To deactivate a team member go to Account - Users and click on the arrow next to the user that you want to make inactive and select "Deactivate". You can also use the deactivate button on the "edit" page for an individual user.
When a user is set to inactive, their access to all of their teams will be revoked (unless they are an account administrator). Their check-in history will be maintained and they can be reactivated by selecting "Activate" from the menu or on their "edit" page.
Your account will not be billed for inactive team members, but their check-in history and metrics will be preserved.