Changing a mailbox from a subscriber mailbox to an information mailbox would require you to delete one in favor of the other but, if you want to temporarily disable the message taking ability you could login to the mailbox, press the admin key, press the greeting key, press the choose key, select alternate greeting, when you choose your alternate greeting mailbox youll be asked if your mailbox should accept messages press the chng key to toggle from yes to no. dont forget to record a alternate greeting for the mailbox.

hope that helps