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.
Google Voice - Google Voice gives you one number for all your phones, voicemail organized in an email format, free...
Signal - Fast, simple & secure messaging. Privacy that fits in your pocket.
Phonebooth - Phonebooth is one of the leading voip providers, providing phone systems & phone service for small businesses.