You can create an unavailable message that plays when your phone goes unanswered and an optional busy message that plays if you are on the phone. 

1. Call the voice mail system (click here for instructions)

2. Log in with extension number and password. 

3. Press 0 to access the Mailbox Options menu.

4. Press 1 to record your unavailable message. 

Optionally, a temporary greeting can be created by pressing 4 at the Mailbox Options menu. If a temporary greeting exists, it will be played instead of any other greetings until it is deleted.