These are three different ways to address messages over the phone:
Enter the extensions of the subscribers.
Spell the first names of the subscribers.
Spell the last names of the subscribers.
In order to address by name, a lettered keypad is required on the phones of the subscribers. This is where those settings can be changed. These are the available options to search by:
Regardless which option is chosen, as subscribers address a message by phone, they can switch between name and extension with either of these key press combinations:
But, when the Enable Spelled Name Search check box is unchecked on the System > Configuration > Settings page, subscribers can only address messages over the phone with the subscriber extensions. Remember that this must be changed on all of the subscribers.