Chevrolet India — Brake problem

I had a brake problem with my Chevrolet Beat Petrol and it was sent to workshop and back and forth with the same problem for few times and recently they have changed brake booster and on the first trip after that the brake completely failed . I did not find any safety in the Chevrolet Beat Petrol i had. Please find the solution or take the car and return the money. (I bought my Car in June 2010)