Asterisk - An open source telephony switching and private branch exchange service for Linux.
RingCentral - RingCentral is the leading provider of cloud-based communications and collaboration solutions for small business and enterprise companies
FreeSWITCH - FreeSWITCH is an open-source media application designed to support popular protools such as SIP and WebRTC and provides a platform to develop voice and video applications.
Nextiva - Business VoIP, cloud phone systems trusted by more than 150,000 companies. Powered by the leading cloud PBX VoIP platform, Nextiva is rated the best business VoIP service provider.
3CX Phone System - 3CXPhone is a free VoIP phone available for Windows, iPhone or any Android based smart phone such...
Aircall - Aircall is a call center software of a new generation designed for fast growing companies. Setup instantly and integrates to your CRMs