RingCentral - RingCentral is the leading provider of cloud-based communications and collaboration solutions for small business and enterprise companies
Mumble - Mumble is an open source, low-latency, high quality voice chat software primarily intended for use...
Dialpad - Switch is a cloud-based phone system built for Google Apps users.
Discord - Step up your game with a modern voice & text chat app. Crystal clear voice, multiple server and channel support, mobile apps, and more.
Aircall - Aircall is a call center software of a new generation designed for fast growing companies. Setup instantly and integrates to your CRMs
GSC - With GSC, you can pick from any of 14 worldwide datacenters to host your own free voice server.