Seller is trying to harm my business, buying and cancelling

A seller is buying my products in bulk and cancelling the order as soon as I ship them, I identified that the seller earlier mapped my brand to their listing, Upon investigation I was able to remove him but now they are retaliating by placing orders in Bulk and cancelling them just to cause harm to the business! I am getting my lawyer involved however what is the best course of action for this as far as Amazon is concerned?