You can block ALL feature codes, require the SPCL key to enter feature codes, then remove the SPCL key from those user's phones. SPCL key is the circle with an X on Mitel phones, SPCL or infinity on Inter-Tel phones. To remove it just program it as something else useful or UNDEFINED KEY. Be sure to give them hard keys for everything they need, though, because the old standards such as 4 for pickup and 8 for outgoing won't work either, then...