This woman was told her mortgage was paid off: 10 years later, she received a foreclosure notice in the mail. She decided to fight.

Rose Prophete bought her home in Canarsie, Brooklyn, N.Y. in May 2005. She thought she had paid off her loans until recently, when a company approached her about a debt she thought she had settled a long time ago.

The company expected Prophete to pay up over $130,000, or face foreclosure.

When refinancing her mortgage on the home, Prophete...