AC is very bad in Tata cars

Mileage is dropping while using ac. AC is very bad in Tata cars, I given my car 3 times to service center but there was no use from service center. I used many Tata car since 2016, initially I thought my car only having this problem. Currently I am using tata nexon this car also having ac and mileage dropping issue. Tata car is only good for safety and exterior design.