Unacceptable Service

I bought a petrol pump at Korean Spares in Lenasia on 03.09.2025. I gave the sales guy my engine number and asked him if it was possible to exchange if it doesn't fit, and he advised that it won't be necessary as he had sold this to me using my engine number. I then went and got the part fitted in my car and my car wouldn't start after that. I called the guy and told him my car won't start with this petrol pump, and he advised that, unfortunately, he won't be able to exchange I must buy another one. My question now is how is't possible that the packaging of the part is reflecting the correct details of the product I want and the product inside is something else? The guy even mentioned that this might be due to a factory fault. Who must pay now for a factory fault? Me?