Bank Accounts can be created or updated, by selecting the applicable Upload Mode. You can refine this by the Country, Bank or Branch. But, if you have a unique Branch, then this can be entered as a minimum. If the Wizard identifies that this is not unique and only the Branch is entered, on validation the Wizard will present a message to further refine your data.
At this point, if only the Bank Account section is uploaded, this will not yet be assigned to a Customer until this is done in Oracle or via the Bank Owner section of the Wizard.