GetChat.App - Add WhatsApp chat to your website for free
Gomix - The easiest way to build the app or bot of your dreams
Smooch.io for Facebook Messenger - Message your customers from Slack, Front, a bot or anywhere!
Chatfuel - Chatfuel is the best bot platform for creating an AI chatbot on Facebook.
Avochato - Text messaging for your business.
Octane AI - Octane AI offers tools to create a bot and engage customers and audience via messaging.