Unable to use keypad numbers on Freestyle 2200

I have recently been given the BT Freestyle 2200 handsets, but seem unable to make any calls, due to the fact that when I press the number buttons, nothing happens.  The keypad isn't locked, as the key symbol is not showing on the screen, and other keys seem to be recognised and working, but none of the numbers work..!  I am beginning to tear my hair out with this problem, and a quick browse through the instructions hasn't helped either.  Any suggestions..??