This is a lie. Never fall for it. When they say the promise is invalid, they mean that the money will be refunded only if it has no effect at all. For example, if they lose weight, they say that they can lose 10 kg, but they only lose 2 kg, and she won't refund you, because it is effective, and if they lose size, there is no guarantee. And they rubbed it so hard that it was all purple.