I recently had a disappointing experience with Nissan Hatfield

I recently had a disappointing experience with Nissan Hatfield. After servicing my car with them, I noticed damage to my instrument cluster when I picked it up. Initially I thought it was just dirt, but upon further inspection, I realised it was a more serious issue. I went to them the following day where the Manager told me I won’t be able to get it off as it was damaged by a chemical and my car wash was probably responsible for it. I told him the damage happened at their branch. He said he would investigate. Luckily when I got to work I realised I have photographic evidence, pictures I took on the morning of the service, and pictures I took of the damage after fetching it from them. I screenshot the pictures so he would also see time stamps on them and then forwarded to him, He said he will speak to everyone involved and give me a call the following Monday. It’s been 3 weeks and he hasn’t kept his word. As of today, I still haven’t received a resolution or communication from them.