Terrible Car Quality

bought a Renault Captur April 2018 and its under service and maintenance plan. Last went for Service in December. Last week Friday, it wrote a message check injection and car could not move faster than 20km/h. My husband took it to the Dealership in Centurion,Waiting for an hour just to be assisted there after i get a call that for them to diagnose the car, R7000 is payable and if its a clutch its R15000. Question is how could they predetermine its a clutch issue before their Diagnosis. I was sent from pillar to post before I could even get policy documents for the maintenance contract. I had to timeously call them to keep updated with the progress of the car and i was met with vague answers not waa i given any documents or anything telling me about the faults or repairs that need to be done on the car. To add a cherry on top to my terrible experience, liquid capital says they will not cover my claim. Big question is how durable are your cars to begin with, Secondly why does one have to pay for diagnosis of the car yet it is your brand and is under warantee do you not take accountability. People thought i was mad to go with such a problematic car brand and this experience further solidifies my deepest regret!!! I will never advise anyone in their sane mind to buy a Renault!