Sub standard treatment at Star Nissan Vereeniging

I was told the water cap needs to be replaced on my Nissan Navara.They ordered the cap and I got the call that the has arrived and I need to book in my vehicle. I did so on an agreed date and fetched the car after being told everything is done. When I got home I checked the water cap only to find that it's the old faulty cap. Mind you they had already submitted the claim with the my warranty provider. I went to complain and seemingly I was a joke at the Nissan office ,people were laughing at me.