Nexmo - Nexmo is a simple two way SMS API with global reach and wholesale rates
Callmama - Get cheap international calling, international virtual number, Call Mama Gives an added advantage to send message and make calls to non-user of Callmama App.
MessageBird - Reach 7 billion phones in seconds via SMS, Chat & Voice. Try it for free and improve your communication.
CallHippo - Easy to use Phone System with World-Class Support
Plivo - Plivo simplifies your customer engagement.
KrispCall - Virtual cloud phone system for business