Discuss with the merchant first, try to be tactful and see if you can refund more money. Of course, this possibility is almost zero, but this is the way to go, and then consult a lawyer. If you go to court, the lawyer will tell you what to do. This is a step for you to defend your rights, but it has been four years, and it is basically impossible to get your claim back. One is that you have no proof, and the other is that you bought something of your own free will. If you buy it wrong, you can only read it wrong. No wonder others are wrong. what do you think?