Hello,
Try configuring the following:
config t
telephony-service
directory entry 1 [ext] name [name]
directory entry 2 [ext] name [name]
and so on and so forth.
Also you can configure how you want the names to appear in the directory:
config t
telephony-service
directory [last-name-first | first-name-first]
Hope that helped, if so please rate.