Regarding the threats, if they are a serious enough to be a criminal offense, you can file a complaint. In any case, contact or go to the competent Gendarmerie Brigade or police station (
click here to find it ). Regarding the product, the customer can always make a claim as it is guaranteed. In this case, inform him of his rights and the means at his disposal to make this guarantee claim work. He may, if he wishes, to take action against you before the relevant court.