Viber is a great solution for audio and video calling. The user interface is very simple and user-friendly. I have used Viber for many years and while using my mobile internet Viber doesn't spend a large amount of data. That is why for voice callingViberr is my first choice. The second reason is that while using my mobile internet I can't make WhatsApp call. My operator doesn't allow this. But with Viber, I didn't come across with this problem.