BMW Donford worst dealer

I booked my car for service on the 2nd of January 2025. The whole time my car was there I was in contact with them and they were also engaging with me and my husband the whole time incase they discover any additional thing that needs to be done on the car , which was fine with me. The car was collected on the same date 2.01.2025. Firstly I saw that the drivetrain error was still there which was concerning to me. I didn't report it as I thought it will maybe go away in a few days. On the 5th of February I was driving to work where I got a notification on the screen about engine oil pressure. I stopped on the side of the road to wait for my husband as this was very concerning. We had to tow the car home. When my husband checked the oil top opening it was so dirty with oil sludge as if nothing was done on this car. On the 6th of February I didnt go to work as I wanted to take the car back to Donford, they told me I can bring the car on Monday the 10th of February. I left the car there. To my surprise I was told I have to pay R5500 for them to check what the problem is. This shocked as I thought this is a return job since my car was serviced by them a few weeks back. I gave them a go ahead to open it up. They called to say the issue was because of the old oil I need to replace the engine. I had asked the money I paid for oil service , what was it for? They can't just take out old oil and add new oil without flushing the old one. Shocked as I was , I asked them as they saw that the car was behind with service and was brought in to be serviced to go back to its optimal condition why didn't they flush the engine oil? Even the system they use should point out the issues , also the person servicing the car should have picked up or suggested what needs to be done to prevent such. At this point they don't care at all and are just telling me to replace the engine. I feel like they are taking advantage and trying to make money out of me.