ausername
These are Open/Closed greetings, note the comment below from the Help. Maybe you could just upload the same greeting for both Open and Closed?
To configure the Mailbox Greetings:
Access the System Administrator's mailbox.
Press [2] for the Edit Mailbox menu.
Enter the mailbox number to edit.
Press # repeatedly until prompted to enter a Technician's function code.
Enter the desired Non-busy option from the table above.
The Technician's function code prompt repeats. Enter the desired Busy option from the table above.
Repeat for other mailboxes are required.
To download an audio file containing a mailbox greeting:
System Audio Files Update form
Select Mailbox Greeting
Enter the Mailbox Number
Select the Greeting Type: Main/Business Open, Business Closed, Temporary, or Name
NOTE: Business Closed greeting is supported only for Multi-level Auto Attendant (MLAA) menu node mailboxes.
Browse to choose the audio file
Click Update