Extremely frustrated

I took my vehicle to Renault Service Centre Tygervalley for a diagnostic check as it was cutting out whilst driving.. They returned the vehicle say they could not find any fault costing nearly R1000.. The vehicle displayed the same fault and was taken in again. Then by luck or chance or perhaps a roll off a dice they said they found the fault. Paid R3700 only for the car to display the exact same problem as before... I take it back only to realize as they want to scan my vehicle that the license disk is missing.. Enquiries at the service center... No luck.. They insist that it was on the vehicle as it is scanned in and out, but could not provide any footage that it was on the vehicle when I collected the car on 12 March 2021.. I cannot fathom how a dealership cannot find a fault on a vehicle... I AM EXTREMELY UNHAPPY WITH THE LEVEL OF WORKMANSHIP. WHY AM I PAYING PREMIUM FOR SUCH SHODDY WORK..