You now have the ability to Deactivate an entire Sub Org from your MobileServe account.  This handy feature allows you to remove all of the users in a specific Sub Org from your organization, freeing up those seats for new users.

To Deactivate users simply go to your Dashboard > Sub Orgs and click "Deactivate" for the Sub Org you want to remove.  Keep in mind that this action CANNOT be undone, so make sure that you are clicking on the correct Sub Org.

Deactivating a Sub Org will only remove the users from your organization.  You will still have access to the data and the logs they created under your organization, and they will still have access to their own logs as well.  However, they will no longer be able to log hours against your organization.