public void StopCall(string sender, string receiver, bool isGroup)
 {
     if (isGroup)
     {
         GroupConversation group = Subscriber.GetGroup(receiver);
         group.UserLeftAudio(sender);
     }
     else
     {
         UserInformation user = Subscriber.getUser(receiver);
         if (user != null && user.AudioCallback != null)
         {
             user.AudioCallback.StopCall(sender);
         }
     }
 }
        public void InitCommunicationGroup(string sender, string groupName)
        {
            GroupConversation group = Subscriber.GetGroup(groupName);

            group.InviteMembersToAudioCall(sender);
        }