Chatfuel - Chatfuel is the best bot platform for creating an AI chatbot on Facebook.
Massively - Create and deploy polished chat bots
ChatBot - Easy to use chatbot platform for business
Bottery - A conversational agent prototyping platform
Landbot - An intuitive no-code conversational apps builder that combines the benefits of conversational interface with rich UI elements.
Dialogflow - Conversational UX Platform. (ex API.ai)