I've got a problem with my s3. When making or receiving a call the screen turns off.
It does this even if the phone is not moved and is just left laying on my desk.
Just before the screen turns off a symbol of a phone handset appears in the left hand side of the notification bar at the top.
If I've made the call I have to reboot the phone to get a working screen back. If somebody has called me, after they've hung up I can get the screen back by pressing the power button - which takes me to the Lock Screen.
That icon mean there's issue with your dialer app. Is your phone stock? I know how to fix it but it needs to be rooted.
You can try clearing the cache on the phone,contacts and google service framework within settings.