Telegram - Telegram is a messaging app with a focus on speed and security. It’s superfast, simple and free.
Twilio - Brings voice and messaging to your web and mobile applications.
WhatsApp - WhatsApp Messenger: More than 1 billion people in over 180 countries use WhatsApp to stay in touch with friends and family, anytime and anywhere.
RingCentral - RingCentral is the leading provider of cloud-based communications and collaboration solutions for small business and enterprise companies
Signal - Fast, simple & secure messaging. Privacy that fits in your pocket.
CallHippo - Easy to use Phone System with World-Class Support