Each mobile phone model is different especially by different brands. I got asked a few things by my neighbors about their phones.
finding dial pad on one phone had to press the (touch screen) phone button then star(favorites) and the dial pad button on bottom.
On one phone to get the power on/off (sleep/wake) button to work had to take off the battery cover and put it back on properly..
On a flip phone had to press and hold the red call end button for about 3 seconds to turn on and off.