Dialogflow - Conversational UX Platform. (ex API.ai)
Nexmo - Nexmo is a simple two way SMS API with global reach and wholesale rates
Botpress - Open-source platform for developers to build high-quality digital assistants
MessageBird - Reach 7 billion phones in seconds via SMS, Chat & Voice. Try it for free and improve your communication.
Messenger Platform - Discovery, chat extensions, and richer experiences
Plivo - Plivo simplifies your customer engagement.