How to manage your users` contacts list?

Is there a way to prevent one user group from talking to another user group?
  1. Go to the Web Control Panel – Settings – Options tab.
  2. Uncheck the box “Any-to-Any contacts” and uncheck the box “Allow Edit contacts”.
  3. Now go to Users tab, click on a user, and go to “Contacts list” tab to manage his contacts list. Users can communicate only with other users that are in their contacts list. So you leave there only the users he is allowed to communicate.