Viber is a free app which allows you to send texts and make calls. The difference between this app and Skype is that the first one is integrated with the address book of the phone. Plus, the app recorded 50 million users. Of course, not everyone is active but the count is impressive. When using Viber, users send almost 1 billion texts each month and talk more than a billion minutes.
The free app is available on Android, as well as on iOS and together users make 150 million calls every month. If we were to make some averages, we can say that there are 3 calls every month made with the app.Read more