VW Princess Benoni

I have a bad experience with VW Princess Benoni. I took my car in so they can adjust the Timing on my Polo. They then called me to tell me they have to take the cover for engineering, They then called and told me I need new bolts and other things.

I then fetch the car and it had a rattling sound. when I emailed them they asked me to come back. When I get there, they told me they can check the car for me but it will cost me R4K.

I have went back again yesterday & they told me they can check the car, if they were in the wrong they will fix it, if they are not I must now pay R5K.

how do I know they they are in the wrong or not because when I took my car in, it did not have A SOUND.

I think this is unecthical. now I am stranded and don't know what to do as it seems I am damned if I do and damned if I don't.