Cracked Screen during first Service

Hi, I took my car for first service on the 24/04/2019 at Wonderboom Volkswagen, when I pick it up later, I drove away for 500M and I noticed that my windscreen has a big crack across, I quickly returned to show them and they waved me away saying it might have came like this, I told them it was never like this in the morning when I drop it. I asked them about their checklist and they said they have not done it. I had not grounds because I had no proof with me, I went back home with my heart sore and the following day I contacted my insurance company to claim and we set a date. it never sat well with me and I wanted justice, I got footage of my car from where I stay to check if I was wrong and still there was no crack, I called VW to make an appointment to speak with the dealer principal and still not win. he told me it must have cracked at a washing bay while they were washing it and after they parked it facing the sun, which I totally disagree because 2 days before my car was at carwash, the crack can not escalate from 0 mm- 1m long crack in 4 hours on a sun,I don't mind replacing it, all I need is justice because this makes me feel like I am ******* and a ****.