Screen turns black during call after adding SD card I have a Colours X120Q (Shine II) running Android 4.2.1.

Phone calls worked fine before I added a SD card in the device, after which the screen started turning black (shutting off) during calls. This behaviour continued even after I removed the SD card. There are no apparent setting for proximity sensors nor are there any options in the call setting of the phone application.

What can I do other than restoring factory settings?
This is expected behaviour. The screen turns off during a call to prevent you from accidentally pressing on the screen.

I don't know if it possible to turn this off without rooting. It seems on some Samsung firmwares there is an option within the phone app but if you have checked there then I don't think it's possible.