3CX
3CX VoIP Phone Softphone for Windows (PC) Setup Guide, This will allow you make and receive calls from your PC or laptop? Look no further! The 3CX VoIP softphone for Windows is a free app developed by 3CX.
https://www.3cx.com/voip/softphone/
Registrar: sip.prod.gradwell.com
Outbound proxy: nat.gradwell.net