Zoiper is a popular softphone client, it has both free and paid for versions to get extra features. Zoiper can be connected to a SIP/VoIP carrier directly, or to an IP PBX system to use for desktop or mobile calling!
* View the Voxtelesys guides here: [https://voxtelesys.com/tutorials/zoiper](https://voxtelesys.com/tutorials/zoiper)