Unfair costing and charging to customer

I called in for support about an amber warning light. Mercedes adviced that my car should get to the workshop. I mentioned it is still drivable at lower speeds. They insisted on using a tow truck. Upon repairs, they charged me for all costs. I felt unhappy because I bought this brand hoping to benefit from its reliability. Now there is a defect which cannot be explained but is attributed to me and I had to cover all cost. Although I did make it clear the car is still drivable but now I must cover everything. A cost of R11k for replacing a part of R500.