VoIP Made Easy
Telephone allows you to make phone calls over the Internet or your company’s network. If your phone line supports SIP protocol, you can use it on your Mac instead of a physical phone anywhere you have a decent network connection.
Telephone is free and all its features are available to you. Please consider buying an optional subscription to make ongoing development possible. You can do that when the app launches first time after an update or by choosing Support Telephone... in the main menu.