Hardware key control mode
If your phone display is damaged or broken, you can answer an incoming call, end a call, or turn off an alarm using the hardware keys.
Turn your phone off.
Press and hold the Power/Lock Key
and the Volume
Keys 
at the
same time for more than 6 seconds to enter the Hardware key control
mode.Press the Volume Keys
to scroll to the desired option,
then press the Power/Lock Key to confirm.Answer a call: Press the Volume Keys at the same time.
End a call: Press the Power/Lock Key during a call.
Stop an alarm: When an alarm rings, press and hold the Volume Up Key or Volume Down Key to stop the alarm.
If you use your phone with a broken display glass, your phone can break even more or you can be injured. Make sure to visit the LG authorized service center to get your phone repaired.