Did you sign an agreement, contract or something before you bought it? If not, that's the problem. Remember to secretly record when negotiating again, collect good evidence and report it directly to the industrial and commercial bureau. Go to them if you have nothing to do. It is best for the industrial and commercial bureau to have an acquaintance to see if there is a formal invoice. You can tell them to report to the tax bureau and deal with such malicious businesses. You don't have to be soft-hearted, do everything possible to get them.