In fact, our research shows there are a good number of apps that say “end-to-end encryption” but they don’t mean device to device. They mean your device to their server, then your call is unencrypted on their server where they can listen or record your call.
True End-to-End Encryption: True encrypted calls will exchange the encryption keys directly between user devices. The server is only there to route the calls across the Internet and through NAT’ed firewalls. Since the keys are generated on the users’ devices and only the public keys are shared with the other user, the provider or anyone listening in the middle can’t hear what you are saying, let alone record it.
Zangi Secure Messaging App is a peer-to-peer (from one device two another), end-to-end encrypted app, encrypting whether 1:1 calls, or group calls. Middleman listening is impossible.