Appaling Service Mercedes Benz Constantia

I book for an appointment online. My vehicle was scheduled for 08:45. I arrived at 9:00. I was advised that am late. The car will not be attended to. I was only 15 minutes late. I was supposed to have been there at 7 am. Online booking time is incorrect, as advised by Kelly. I advised her that it's fine, can I get my vehicle the next day at 1pm. She said she'll try. I only got a call from her the next day shortly after 11am regarding the quote. I asked her will the vehicle be ready at 1pm as per yesterday request. She said no. My vehicle was there on Thursday, and Friday half day without being touched. I received an email from her at 16:46 advising that the vehicle will be ready on Saturday. I called the dealership after 9, on Saturday. I was advised that the place is closed. No one is at the dealership. This kind of service is appalling. I want to know why the vehicle was not touched on Thursday as I only arrived 15 minutes late, why only on Friday after 11. Why did Kelly advised that the vehicle will be ready on Saturday knowing very well that customers are not serviced on Saturday? Incorrect mileage and date of last service is incorrect on the invoice. This was addressed last year, but never rectified. If Mercedes Benz Constantia does not want me there, they must let me know. I don't take kind to this kind of service.