Prepayment Account default

The prepayment account default defined in the Financial Options was assigned to Suppliers / Supplier Sites as they were created.  We've recently updated the account default in the Financial Options due to a business change, however, when we enter a prepayment invoice for a supplier that already had the original account defaulted, it's using the account from the Supplier Site and not the Financial Options to create the invoice distribution.  When I look at the Payables Options to see if there's a setup change available, I only see an option to use either the Supplier Site or a Purchase Order