Well sir, if you knew the law, why did you ask our opinion? It's true, that is what the law says. However, have you ever wondered how someone gets away with saying, "We have the best burgers in the world!" When they don't necessarily. I'm not saying you don't have a case, the fact that they changed their sign says that you hit pretty close to home. However, the idea that they are a business means they can't charge Zero percent on every loan all of the time. It isn't a believable advertisement and they can't be held to it. You are free to sue them, I imagine you will recover something. Their advertisement isn't very bright either.