There are many factors that can influence the KSAFone calling performance: network connection, sound card drivers, headphones quality and so on. In order to fix the issue, I suggest you both close all unnecessary applications that use the Internet bandwidth and stop any file downloads. Also, update your sound card drivers and use a quality headset with a built-in microphone. If the problem persists, download and install the latest version of the software. Alternatively, you can use another VOIP program from Software Informer database.