letter of complaint

I v been treated badly and taking advantage because I am woman. Bought the car in2014 then after 8 months car start pulling to right side I reported but they gave me bad attitude saying nothing wrong with the car other mechanic advice me to do shock test all shocks were weak but them don't want to take responsibility even the car was still new and I'm paying.in2015 they give me another car saying new car then started new instalment again and within 3 months car start pulling again then reported promise to replace new shocks but car still pulling. Then did other shock test still show shocks are weak when I told branch manager he said to me take another new car then start new instalment and I ask again then he said must take the car and leave and if I leave the car with them they will take it out to the pavement because it is not their car what I'm asking is it right to talk to the customer like that as now I'm preparing to use my money to replace new shocks because they failing to do that.