3CX is recommended for small to medium-sized businesses, enterprises looking to integrate their communication systems, and organizations that need a scalable and flexible telephony solution. It is also suitable for companies wanting to enhance their remote work capabilities with features like web conferencing and mobile app 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.
Linphone - Linphone is an internet phone or Voice Over IP phone (VoIP).
Aircall - Aircall is a call center software of a new generation designed for fast growing companies. Setup instantly and integrates to your CRMs
Zoiper - Cross-platform VoIP softphone dialer for SIP and IAX systems
freepbx - FreePBX is a web-based open source GUI that controls and manages Asterisk (PBX).
Sipdroid - Free and open-source SIP/VoIP Client