Twilio - Brings voice and messaging to your web and mobile applications.
Dialogflow - Conversational UX Platform. (ex API.ai)
Swift SMS Gateway - SMS Gateway is your bridge between the Internet and the world of cell phone SMS text messaging.
Octane AI - Octane AI offers tools to create a bot and engage customers and audience via messaging.
Maytapi - Serverless Whatsapp Api with Chat and Agent support.
Microsoft Bot Framework - Framework to build and connect intelligent bots.