I have a samsung genio touch how do i access the keypad during a call

On the right hand side of the phone, in just about the middle, is the button that's used to lock the phone.
When you make a call, once the ringing tone can be heard, press this button and hold it in until the screen changes.
One of the options on the new screen will be keypad (bottom left). Another option will be loudspeaker.
Hope this helps.

To be able to use the keypad when you are in a call you need to unlock the touch screen. To do this, press the lock symbol (found on the right hand side of the phone) during a call.