Bad service

On the 09 of Feb 2018 I took my car to VW Mtata for them to fix my car the problem was that the stirring wheel had locked and the car keys we broken...They said for them to fix the car I must leave behind a deposit of R3000. They took days not getting back to me with regards the progress I kept on phoning them checking how far are they with fixing the car. When I went to take the car they requested that I pay an amount of R3500 on top. They didn't assemble the car for me I then realised that the car is not locking,when asking them no one gave me a straight answer yet my car was locking when I brought it to them. Your assistance in this regard will be highly appreciated. Thanks **********