why does a vertical red line appears on my phone

[charminogue]

When I am talking on my lgk30 the screen flashes with a red vertical line gong down the screen. Then when I try to end the call I can't and just have to wait for the phone to eventually ends the call. I sometimes use the **** down phone function and then cancel as that will stop the madness.

 

[Rukbat]

That sounds like a screen overlay from some other app. If you tap the hangup icon, the call should end (if the screen is overlaid by something, that won't work).