Twilio - Brings voice and messaging to your web and mobile applications.
Plivo - Plivo simplifies your customer engagement.
Maytapi - Serverless Whatsapp Api with Chat and Agent support.
Nexmo - Nexmo is a simple two way SMS API with global reach and wholesale rates
Swift SMS Gateway - SMS Gateway is your bridge between the Internet and the world of cell phone SMS text messaging.
HeyWire - Next-level customer service is just a text message away.