With Partner Messaging, you can assign an auto attendant to a mailbox. Then assign the selector codes to guest mailboxes.
For instance, the phone that the 4 people use is Ext. 20
In Partner Messaging, create Mailbox 20, assign it to Auto Attendant No. 4. Create mailboxes 41, 42, 43, and 44, WITH a phone. In the ACS, assign Auto VMS Coverage to 20, 41, 42, 43, and 44, set the VMS Coverage Rings for 20 to the regular 3 or 4, but set 41, 42, 43, and 44 to 1.
in Auto Attendant No. 4, set it to follow the Weekly Business Schedule, closed all days.
In the Night Menu of Auto Attendant No. 4, make Selector Code 1 do a mailbox transfer to mailbox 41. Selector Code 2 to mailbox 42. 3 to 43, and 4 to 44. Make the Dial-0/Timeout option transfer to Ext. 20.
Record the AA-4's Night Greeting the say "For Fred, press 1; for Barney, press 2; for Wilma, press 3; and for Betty, press 4"
None of these people will have Message Waiting lights - they will just have to check from time to time for messages.
If you have an ACS R7, release O, or ACS R8, you can add a button for 41, 42, 43, and 44, and a Message Waiting Status button.
You can transfer callers directly to the 4 mailboxes, or to 20 and let the caller decide who they want to leave a message for.