Hud Refinancing How Does This HUD Payback Work?

How does this HUD payback work? - hud refinancing

In 1998 I bought my first home ... My mother was tha co-signatories. With about six miles have my apartment. My previous band was oldkent Mortgage, based in Cincinnati. In 2000, the bank merged 5th3rd. Two years ago, the refinancing and repayment. FHA / HUD Sixthousand send you an invoice that I owed them. 5th3rd I called the bank and a letter that the account was paid. I recently sold my house and now again asking HUD for money. Now they want to just see a canceled check. The problem is that the bank is able to locate any payment. They sent me and my mother's collections. Not any suggestions? Why should I pay the FHA or HUD?