A horrible service done on the car.

On the 29th/09/25, I took my car to service at 85376, Job card 19974. They did not check everything and I had issues with the car days later when I drove the car, as I work from home. The engine light came on and I contacted them. They told me to bring back the car, I did and they kept it for 2 days. They told me spark plugs have erosion, even after I have told them I do not wash the engine, my chat is why did they not notice this on the 1st service? They did a horrible job and they put my life in danger. Now they claim spark plugs are not covered and I need to pay to replace them. However, on the warranty book spark plugs are included and says it should be replaced at specific intervals and does not say anything about paying. So I am taken for a fool. I was also advised I will be called a few days after I fetched my car because they had claimed something that was under warranty and it will be replaced. I am driving up and down a car that might breakdown due to incompetence of the technicians there. The replacement of the spark plugs is on 8.2.