Terrible service received by BMW repair centre!

On 1 January 2015 I was involved in a motor vehicle accident with my Mini Cooper S. We have never had problems with the Mini Cooper prior to the accident. Auto Atlantic, Milnerton, was responsible for the repairs. We got the car back and less than two weeks later the car started heating up. I immediately phoned Auto Atlantic and they collected the car. The same day, a lady by the name of Melanie called me and said that it appears that a gasket blew and that it seems like this has happened after they fixed the car, or that it may have been an old problem. I told her that was impossible as there was never anything wrong with the car before. She insisted it either happened after they repaired the car or that it may have been there before. It is concerning to me that they are giving conflicting stories about how and when the gasket blew? I have spoken to a few BMW experts and they all agree that it definitely is directly related to the accident. Since then I have not heard from Auto Atlantic. I am severely inconvenienced with no car and have not even been offered a courtesy vehicle. This is the first time I have ever experienced such poor pathetic customer service from BMW.