#Jami is a free open source privacy-conscious alternative to Skype. Jami has no servers, calls are encrypted peer-to-peer, with personal data stored only on the devices making the call.
It's available for Android, iOS, Windows, Mac and Linux from its official site:
You can follow it on here:
Jami used to be known as "Ring", and has very recently changed its name. You may see both names used during the transition period.