[AC Question]

Somebody suggested me that if this problem occurs, then switch off your mobile and again switch it on. But this is not the way. Why this problem occuring very often.

[AlphaTango414]

What do you mean by blank? Your device screen will turn off if you place a call and put it near your head. (Proximity Sensor) When you take your phone away from you head the screen comes back on. However tho, some phones can get hung up and you have to push a button to take the screen back up.

If simple reboot didn't help, boot into recovery and wipe system cache.

[nahoku]

Are you talking about the phone going blank while you're talking on the phone? When is the phone going blank? When you're dialing? Please provide more information.