Hyundai Motor India — damage in service

Address:

Gurgaon, Haryana

I sent my hyundai excent car no. Hr26cg8402 for service on 26/09/18 to superon hyundai, sec. - 37, gurgaon. At that time my a/c was running very smoothly and was very effective. But when i received back the car in the night i found the a/c was not working at all. I sent the car back on 27/09/18 in morning to superon hyundai and they are asking me to pay another six thousand rupees for the repair of the a/c.
Why i should pay for something which was working smoothly before service and got damaged during the service.