Twilio - Brings voice and messaging to your web and mobile applications.
RingCentral - RingCentral is the leading provider of cloud-based communications and collaboration solutions for small business and enterprise companies
Google Voice - Google Voice gives you one number for all your phones, voicemail organized in an email format, free...
CallHippo - Easy to use Phone System with World-Class Support
Phonebooth - Phonebooth is one of the leading voip providers, providing phone systems & phone service for small businesses.
Aircall - Aircall is a call center software of a new generation designed for fast growing companies. Setup instantly and integrates to your CRMs