Twilio - Brings voice and messaging to your web and mobile applications.
Google Voice - Google Voice gives you one number for all your phones, voicemail organized in an email format, free...
Plivo - Plivo simplifies your customer engagement.
Mitel - Business Communications and Collaboration
MessageBird - Reach 7 billion phones in seconds via SMS, Chat & Voice. Try it for free and improve your communication.
VoIP.ms - VoIP.ms is a VoIP origination and termination tool.