Don't want to give my deposito back

I bought a car at NO FINANCE CARS. ..from the beginning the car was not right...they even stipulated it on the contract...i phoned them..send e-mails...no reply's...and no fixing of the car. Then I decided to give the car back!! Now they say I did BREACH OF CONTRACT!....But it was them ...they did not fixed the car..like they promised...the don't want to give my deposto back!!