The industry’s largest lender has switched gears rather dramatically, announcing plans to radically alter the way it sells a controversial insurance product. "In the coming weeks, we are going to stop offering single premium credit insurance on mortgage loans," said Citigroup chairman and chief executive officer Robert Willumstad in a letter to employees last week. Willumstad defended the "important benefits" of the product to many borrowers. But he acknowledged that, "few products in our industry