RebTel is described as 'Free calls to Rebtel users and cheap international calling to everyone else – Use WiFi, 3G or local minutes to make calls ** Features ** - Low-Cost Calls to Any Phone Open the app, browse your native address book, select any contact with a phone number and get started' and is an app in the Social & Communications category. There are more than 50 alternatives to RebTel for a variety of platforms, including Android, iPhone, iPad, Android Tablet and Online / Web-based. The best alternative is Wire. It's not free, so if you're looking for a free alternative, you could try WhatsApp or Hangouts. Other great apps like RebTel are Zulip (Free Personal, Open Source), Viber (Freemium), Whereby (Freemium) and aTalk (Free, Open Source).
Wire is the most secure collaboration platform featuring messenger, voice, video, conference calls, file-sharing, and external collaboration –all protected by the most secure end-to-end-encryption. Why Wire?
WhatsApp is an iPhone and Android messaging app which allows you to exchange messages without having to pay for SMS. In addition to basic messaging WhatsApp users can create groups, send each other unlimited images, video and audio media messages.
With Viber, everyone in the world can connect. Freely. More than 460 million Viber users text, make HD-quality phone and video calls, and send photo and video messages worldwide over WiFi or 3G - for free.
aTalk is an XMPP client that supports the following features: * Instant messaging in plain text and End-to-End encryption with OMEMO or OTR * OMEMO encryption is available during multi-user group chat session, giving users maximum privacy and security * Supports both voice...
Daily is an audio and video API. Easily build video chats in your web or mobile apps with an API built on top of WebRTC or drop in the Prebuilt UI for fast video conferencing integration. 1,000 person video and audio calls. HIPAA compliant.
Fully open source instant messaging server and clients. No proprietary components or non-free dependencies. Backend in pure Go (GPL 3.0), with a command-line administration tool in python + gRPC. Clients for Android, iPhone, and Web - ReactJS (all licensed under Apache 2.0).