messed up my car

Not good experience,took my car for a heater to be fixed bu the car came with a different fault. i told them there was a problem with the car as you drive it sometimes needs to accelerate more, they checked and said i should take the car to a gearbox specialist, when i took my car it was driving fine and never had a problem with a starter, now its dead it doesn't wanna start at all,. They are now denying the fact that there is something that they did to my car as they claim they only worked on the radiator nothing else. I'm not going there anymore.