All Fongo supplied Grandstream and most approved BYOD Desk phones in Fongo Works Pro have the ability to view the Business Member Directory within the phone itself.
For most Grandstream phones the business member directory is merged right into the contacts list. Just tap the directory button on the phone or the contacts screen through the menus.
The functionality for other devices may vary but in general its pretty consistent.
Tap the Directory button on the phone.
The member directory may contact the Fongo Works members.
If you are presented with an option to choose which phonebook scroll down to 'Remote Phone Book' or 'Fongo Works' and select it.
From there you will see the business member directory and can place a call easily to any other member as well as see their extension number.