Audi India — defected a3 with faulty ac

We had purchased audi a3 4 years back. Since then we are facing ac concerns. The ac stops working every year and we need to send the car to their workshop where they change the compressor or cooling coil every year. This year they are demanding huge amount of money saying that the car is in 5th year, ignoring the fact that the car goes to their workshop for the same concern every year since the starting.