You can't connect to Nimbuzz or Fring through Avon Dialer. Nimbuzz and Avon Dialer are standalone, VoIP (Voice Over IP) applications. Fring is an instant messaging application only for mobile platforms. In order to use any of them, you need to create a separate account. You can't connect to one through another. Also, you can't use one application to communicate to a person that is using a different program.