CloudVoice offers the ability to call another user without knowing their extension by using the dial by name directory.
Calling using the company directory:
Dial *411 and press the send button.
A prompt will ask for the first few letters of the persons first or last name. Enter that information.
Dial *411 then press Send.
The most relevent option will be offered. Press 1 to connect to that extension.
If this is not the extension press 6 for the next name in the directory.