Samsung Memoir SGH-T929

When I dial any phone number after the call connects the keypad goes blank and I can not access any of the functions (ie like pressing #1 on an 800#)

I have gone into menu, phone settings, auto keypad lock and turned it off and I have gone to menu, call settings, automatic screen lock and turned this off

neither seems to work.. any idea how I can keep the key pad on while placing calls?

thanks in advance