Mercurius Motors Polokwane damaged my car

I called to report leaking coolant. They told me to keep filling it up and bring it when I can. I had explained that there were no warning signs or overheating engine. I took it 2 weeks later, still with no warning signs or trouble driving. They assessed the vehicle, giving me a quote of over R26000. I rejected the quote, opting to take the car for repairs at another dealer. They said they would put the car back as it was, as they had taken things apart to see the fault. When I picked up the vehicle they said it's not drivable, which doesn't make sense since I drove it there with no problems. I drove less than 30kms then it gives me a Check Engine warning light. This was not there when the vehicle was delivered. I didn't receive explanations for this and had to spend R6000 to tow the car away.