Tata Motors — i'm complaining about your tiago car's main security feature seat belt is not working properly

I'm a customer of tata tiago since 23/11/2016. My tiago car met with an accident on 28th may 2017, 2:30am. At that time 3 passangers inside the car three of them were with seat belt but driver and co-driver's (Me and my wife) seat belt is not locked properly according to that my chest hited by steering and also my wife's head hited on front glass itself before came the air bag. So air bag and set belt were nit worked properly.
Second time i'm having issue with your car and first time issue is one of your authorised dealer rf motors
Now the car is at mk motors, kottayam, kerala. I explained this issue to them, but they replied that "we are helpless, only we can check the seat belt properly or not"
How can i drive this car again. No security for our life.
I request to replace the car. Kindly resolve my complaint as early as possible.

Engine no: revtrn02ktyk24393
Chasis no: mat626281gkk40500
Registration no: kl-04-ak-3202
Selling dealership: m. K. Motors, kottayam, kerala
Car last attended by (Dealership): m. K. Motors, kottayam, kerala
Car presently at: m. K. Motors, kottayam, kerala