Dialogflow - Conversational UX Platform. (ex API.ai)
Telegram - Telegram is a messaging app with a focus on speed and security. It’s superfast, simple and free.
Telegram X - Meet Telegram X for iOS and Android – two new official apps that offer more speed, longer batter life and smooth animations.
Botpress - Open-source platform for developers to build high-quality digital assistants
WhatsApp - WhatsApp Messenger: More than 1 billion people in over 180 countries use WhatsApp to stay in touch with friends and family, anytime and anywhere.
Expensive Chat - Chatroom where you pay per letter