I am cosigner for son's loan with Sallie Mae. Currently a draft amount $293.41 from my account on 26th monthly being made, for over one year. Yet Sallie Mae continues to say the account is past due, and therefore late fees are being added. Bank statements validate drafts.
Have you tried asking Sallie Mae how much it would take to bring the account current? That way you should be able to determine whether or not you agree with them regarding whatever payments that they allege have been missed.
Read the statements and see how much is due. Ask them for an accounting. Have you contacted them to discuss?