Hi,
I tried to check the given directory/file ( /usr/share/jolla-settings/pages/jolla-voicecall/voicecall.qml) from your comment, but could not find on my C2 (v.5.0.0.43). Could you give me some hints or links about locations of setup files (in general) and Gconf variable names of SFOS. I could not find a decent info about it.