Jitsi

If you want to have a private video call without having to worry about being spied on, the service Open Source Jitsi is a great substitute for other, less secure VoiP services.

This chat and videoconferencing client encrypts all sent data, such that any call – whether audio and video – or chat is kept completely protected from any other parties that might want to access your data.

Jitsi can make audio and video calls, record the phone calls you make, and serve as an instant messenger for chatting with your friends, even with several users. All this data is encrypted and encoded using OTR.

Another great feature of this tool is that it's compatible with ICE and TURN. In addition, it improves call quality by suppressing background noise or echoes, making communication more natural and fluid, without audio problems.

Jitsi doesn't just encode your messages and calls, but also looks after all of your security, storing your passwords, which are encoded and protected by a master password.