Authorization Letter. MV-466. Just call 555-5555 and our customer service representative will honor your request.The amount I overpaid was minuscule and the effect is the loan was paid off faster. For ACTIVE faculty, staff and students for an overpayment in the Current Calendar Year. Writing an effective "Inform a Customer of an Overpayment" letter can be challenging, especially if you're not sure where to start. We're making it easier for your clients to receive, complete, and submit important documents using their personal my Social Security account.