Ureliable and Bad service

I've rented a car from No Finance Cars as from 2016 and now I have finished and they had provided me with paperwork. I went to the traffic department twice to do change of ownership, but unfortunately it was a waste of time as they haven't marked the car sold. And when I contact them they ignore me. Right I'm stuck with a car that doesn't belong to me as it's still in their name.