Since you did not provide the plaintiff’s patent number and detailed pictures of the defendant’s products, I cannot give you specific handling advice.
However, you can mainly consider the following aspects of defense:
1. Is there evidence to prove that the product was purchased legally from elsewhere?
2. Can you prove that the product you are using is an existing design?
3. Is there any chance of invalidating the plaintiff’s patent rights?
Of course, we must also be prepared for reconciliation