Asterisk - An open source telephony switching and private branch exchange service for Linux.
Five9 - Five9 provides cloud-based call center software for sales, marketing and support.
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.
Ameyo - Ameyo is a powerful and highly flexible IP-based contact center software that lets you have a personalized interaction with every customer across multiple channels, thereby driving customer engagement to a level par excellence.
freepbx - FreePBX is a web-based open source GUI that controls and manages Asterisk (PBX).
NICE inContact CXone - CXone is a fully-integrated and open cloud contact center platform combining the industry’s leading Omnichannel Routing with the foremost technologies in Workforce Optimization, Analytics, Automation and Artificial Intelligence.