Everyone is using now a Smartphone and many are using as operating system Android, so is nice to know how to stop the screen turning off during a call or why your device display not turning off during calls .
So staring with the first problem regarding knowing how to stop the screen turning off during a call is a the easy one.
To stop the screen turning off during a call tap Menu, settings, and in Calls uncheck “Auto screen off during calls” .
The second problem with display (screen) not turning off during calls is much complex and the problem may be fixed different from phone to phone .
First you need to know if is a hardware of o software problem.
You can verify the proximity sensor of your phone, depending of the manufacturer for example on Samsung devices (S4) type the code *#0*# and it will pop up a windows with all settings, tap on Sensors and there you have the proximity sensor. Move you hand over the front speaker and the phone should vibrate and the screen should turn green, after hand remove should stop vibrate.
If the phone still vibrate and screen is still green after you remove the hand over the speaker proximity sensor has issues. You can try blowing into the speaker a few times to remove dust or to remove the screen protector and then try again (this solved a problem) . If this doesn’t help the sensor is broken .
If the sensor works ok, the problem is software one. It may be caused by an application or something else.
First you may need to restart you phone and try again. Then you need to disable as much applications you can and then try again because some apps are using proximity sensor to work properly .
I hope this will help you !