Tata Motors — Vehicle inconvenience

We had purchased the Tata INTRA V10 from Vaishnavi motors, bulandshahr.
Vehicles registration number UP13BT8607
All services have been carried out thro VAISHNAVI MOTORS unit in bulandshahr 203001.
The vehicle had mileage problem for August from that problem, the service provider check the car inspite of fixing the mileage the mileage has been decreased.
After the 5th service, car iis facing too much problems like
1. Turbo charger
2. Exhaust pipe
3. Silenecer.
And 4 . Mileage
The service provider is also not helping in full support to check the vehicle... it's not even a year that we bought that vehicle.
From above statement it clearly shows that vehicle isn't working properly after the service
So kindly help in that.