SMG Century City ***** Workshop

I have been driving BMW for quite a while having serviced my car at only reputable agencies and providers. 2 Weeks ago however after having done an oil service at SMG Century City, I noticed my radiator was leaking. Normally I would assume age has contributed to this but after discovering water being used as coolant it was evident that something had happened. all my coolant had miraculously converted into water. Strange thing about this is that I don't use water in my cooling system, anyone who owns a bmw knows this. My suspicion was that someone removed my coolant but why. So i began thinking maybe this was done to grab a second hand radiator, remember my car is in mint condition. So I requested video footage from SMG, they politely said sure. I asked when and they said they will let me know (as per Johannes from SMG). This never happed and the issue was escalated. Today a call from a Service Manager who decided to argue with the customer, what an idiot. Warren the SM needs to learn how to chat to customers, he was already on the defensive, I am beginning to suspect SMG Century City found video evidence and dont want to show me anything. I will never take any vehicle of mine to SMG Century City, their response indicates they are hiding something