SOUTH COAST VW. MARGATE. KZN. THEY WANT ME TO PAY DIAGNOSIS FEE BUT THEY COULDNT DETECT WHAT MADE ME TO BRING THE CAR TO THEM

My car showed a coolant light and they towed it in to South Coast VW last week Wednesday but to my surprise they called and said that their machine detects nothing of some sort , I then told the service agent to ask one of the mechanics to drive it around cause when the car has been stopped for a while it wont show until you drive it around. now they want me to pay for the diagnosis fees of R1630 for the things that the insurance are taking care of cause someone bumped to me at the back so my right tail light needs to be changed cause the globes aint working and they have a rust and my speed sensor/abs light is on , of which these things have nothing to do with the coolant and I was aware of them when my car was towed and it has nothing to do with them only my insurance will cover that. They even made a qoute for me for those repairs and I told the service agent that my insurance company will handle it cause I was bumped at the back and now they want me to pay the diagnosis fee of something that has nothing to do with them.