Secret Messenger is described as '• NO FEES: Secret Messenger uses your phone's Internet connection (4G/3G/2G/EDGE or Wi-Fi, as available) to let you message and call friends and family, so you don't have to pay for every message or call.* There are no subscription fees'. There are more than 100 alternatives to Secret Messenger for a variety of platforms, including Android, iPhone, iPad, Windows and Android Tablet. The best alternative is Telegram, which is free. Other great apps like Secret Messenger are Signal (Free, Open Source), Element (Freemium, Open Source), Skype (Freemium) and Tox (Free, Open Source).
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.
Skype is the most popular free voice-over IP and instant messaging service globally. It allows users to text, video and voice call over the internet. Users can also call landlines and mobiles at competitive rates using Skype credit, premium accounts and subscriptions.
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.
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.