Well, what voice mail and which Partner version do you have? You can certainly use a mailbox to provide information, and can have the receptionist (or any other phone user) or the auto attendant transfer to it. Depending on the voice mail, the mailbox can be set to NOT receive messages, just play a message and hang up if the caller doesn't press 0 at the end to transfer back to the operator, or perhaps it can be set up as an auto attendant that can use submenus and announcements to provide more information for the caller.