Car service city fourways is sucks

My car has a problem with "restricted performance" and I booked in Car service city Fourways

They advised me to attend "engine harness" and charging over R8k

When they said car Is ready for collection, I found nothing has been changed, even got worse and they took my money

They refused refund my money as my car not fixed and advised me another part to be replaced which cost over R9k

I can't trust their advise as they failed to deliver good quality of service