ignore the lawyer

he doens't have your product in hand and he can't prove you are selling fake ones. so ignore him. he is just trying to scare you and get some money hopefully, but he won't sue you. if, on the other hand, you are selling more than 1, and sold some before, if he has bought one from you and have it in hand, you need to consult a copy rights lawyer. but first check to see if this lawyer is real one, but not pian zi.