Если ты про Whatsapp, то вот:
°WhatsApp is a popular free instant text messaging system for mobile and other platforms with support for voice and video. Allows you to send text messages, images, videos, audio and electronic documents over the Internet..
°By April 2012, 2 billion messages were sent daily via WhatsApp. more than 10 billion in August 2012. more than 27 billion in June 2013 and more than 50 billion messages in March 2015. In February 2018, about 1 billion people sent 55 billion messages per day via WhatsApp
According to a statement published in the Financial Times, WhatsApp did the same with SMS as Skype did with international phone calls. As with Skype, the program must be installed on both the sender and the recipient
In February 2014, WhatsApp CEO hinted that it was planned to add the functionality of VoIP calls between users by the summer, and at the end of March 2015 this function was implemented on the Android platform.