"I bought my house in June. In October, I made my mortgage payment to XYZ Mortgage as usual. A few weeks later, the payment was returned with a note saying that my mortgage had been sold to ABC Mortgage. However, when I contacted ABC, they said they had no record of my mortgage. I have not made my payment for October or November, and my December payment will shortly be due. I have an escrow account for the payment of taxes and insurance, but I just received an overdue notice from the tax department … What should I do?"