The other party insists on selling it to you because they think you may become their customer. This is why they burst out with such great enthusiasm. You should let them know from the beginning that you are a firm person, and you will not sign up for various remedial classes. Be firm and polite, because refusing doesn't mean disrespect for others. When the other party hits a wall with you many times, make sure you don't sign up, so you won't sell it to you often.