Install twinkle by entering the following commands in the terminal:
sudo apt update sudo apt install twinkle
Description:
Voice over Internet Protocol (VoIP) SIP Phone (GUI)
Twinkle is a soft-phone for making telephone calls over an IP network using the SIP protocol. You can use it for direct IP phone to IP phone communication or in a network using a SIP proxy to route your calls. Notable features include multiple active identities, call transfer, call rejection, 2 simultaneous calls and 3-way conference calls. . This package contains the graphical interface.
Homepage: http://twinkle.dolezel.info/
Version: 1:1.10.1+dfsg-3
Section: universe/comm