Consumer Redressal

Hello, I have placed order for fitness product(rubber dumb bells) and I have received the product that is of very poor quality. The product image that is shown online is not matching with what I have received and it is in damaged condition(cracks) and smelling a lot. I have complained to the online store but they are taking it easy, laughing at me and not replying properly. I have the invoice with me, please tell me how to sue these people. Regards, Muhammad Ali