Smooch.io for Facebook Messenger - Message your customers from Slack, Front, a bot or anywhere!
Gomix - The easiest way to build the app or bot of your dreams
Intercom - Intercom is a customer relationship management and messaging tool for web businesses. Build relationships with users to create loyal customers.
Chatfuel - Chatfuel is the best bot platform for creating an AI chatbot on Facebook.
Sparkcentral - Good old fashioned customer service, delivered in a high tech way
Octane AI - Octane AI offers tools to create a bot and engage customers and audience via messaging.