Dickens himself experienced this hardship as a child when he was forced to work in a boot blacking factory after his father was sent to debtors' prison.
Primarily, the banker-customer relationship is that of debtor and creditor -- who is which depending on whether the customer's account is in credit or is overdrawn.
In sum, as college student debtors and banks have signed agreements concerning repayment of the loans, banks are entitled to publicize graduates' default as is stipulated in the agreements.