Car got scratched and BMW refuses responsibility

'I took my car for service on Wednesday 20 September 2017. They did everything updating me. On collection of the car the service advisor Michelle did not call me but the driver did, when I got to the dealership Michelle did not give me the keys but walked away, she did not go to the car with me, the guy who gave me the key told me that everything on my and on their system was fine. I drove home where I arrived in 10 to 15mins. I called the dealership after seeing the scratch on my car. They said I come in the morning and I did. When I got there the so called manager of service came to me and told me that they don't take responsibility because the car left the premises.

I was trusting them as professionals and my trust made me not doubt them'. The events as explained by my husband who took in the car for service.