Astian Spika is described as 'instant messaging service focused on speed, security and productivity. With great differences such as integration with Astian Cloud, support for video calls, calls among other features' and is an app in the Social & Communications category. There are more than 100 alternatives to Astian Spika for a variety of platforms, including Android, Windows, Mac, Online / Web-based and iPhone. The best alternative is Telegram, which is free. Other great apps like Astian Spika are Signal (Free, Open Source), Element (Freemium, Open Source), Jitsi (Free, Open Source) and Slack (Freemium).
Signal is a messaging app with an unexpected focus on privacy, combined with all the features expected from a modern IM app. Signal has received a lot of praise from all around the world for its security and privacy-respecting technologies.
Element is a secure collaboration and messaging app based on the Matrix protocol. It’s decentralised to deliver digital sovereignty, and based on an open standard for easy connections and interoperability. It is end-to-end encrypted by default.
Jitsi (previously SIP Communicator) is an audio/video and chat communicator with full encryption that supports protocols such as SIP, XMPP/Jabber, ICQ/AIM, Windows Live, Yahoo!, GTalk/Hangouts extensions, as well as OTR, ZRTP, etc.
Slack is a unified communication platform built with an optimized workflow to keep modern teams focused and productive. A familiar chat interface facilitates discussions while advanced features are easily exposed based on context.
Matrix defines a set of open APIs for decentralised communication, suitable for securely publishing, persisting and subscribing to data over a global open federation of servers with no single point of control.
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.
Pidgin is an easy to use, multi-protocol chat client client used by millions. Connect to AIM, MSN, Yahoo, XMPP, and more chat networks all at once. It has built-in support for NSS, offering client-to-server message encryption for protocols that support it.
Jami (formerly GNU Ring, SFLphone) positions itself as a potential free Skype replacement Open Source and cross-platform. Jami gives you a full control over your communications and an unmatched level of privacy.