The invoice, in a white business envelope with a window on the front, looks legitimate. The first indication something is not quite right it is the postage mark indicating it is pre-sorted bulk mail – unusual for an invoice. The document itself, purporting to be from US-Telecom, looks like a standard invoice with your firm’s name and address, a reference number and a notation that you owe $425 for a Telecom Maintenance Agreement with the terms listed as “Net 30 Days.”