i have not found "dialpad on during every call' setting, there was only Settings->Call settings->Show dialpad->All calls;
however, i tech suggested to check the Settings->Display->Brightness unselect Automatic and set the bar level to the max or near. I think b/c the sensor that is located near the front camera is reacting to the light, in the darker room doesn't respond to well. So far, my issue with the dark screen on a call-in, call-out is fixed. However, the promptness of the display screen to come back is a bit slower than the other phones. Verizon rep confirmed it.
Good luck to all of us!