Telegram - Telegram is a messaging app with a focus on speed and security. It’s superfast, simple and free.
RingCentral - RingCentral is the leading provider of cloud-based communications and collaboration solutions for small business and enterprise companies
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.
Dialpad - Switch is a cloud-based phone system built for Google Apps users.
Signal - Fast, simple & secure messaging. Privacy that fits in your pocket.
Aircall - Aircall is a call center software of a new generation designed for fast growing companies. Setup instantly and integrates to your CRMs