A bit. If you go to Tables- Practice- Practice Preferences and choose the Statements tab, you can edit the dunning message. You don't have many characters and it's only by aging date, but it can be edited. If you want the whole aging box to go away, that's not possible.
I just found another way to add a customized note to a statement, though this would be patient-specific, not on all your statements like my above reply. In a patient account, right click up in the top demographic info area. Under Miscellaneous, there's an option for "statement note". This prints on the very bottom of the statement up to the expiration date you are required to specify. Hope this all helps!