overcharged for repairs on a new car

My mom bought a new Opel Corsa Ecoflex in August 2019 at William Hunt Midrand the sales consultant who assisted was Meshack Ngubane .On the 17.01.2020 the car gave problems and she took it back to William Hunt service department ,they told her that the clutch was the problem and that it will need to be replaced .They will order the parts and will get them Wednesday 22.02.2020.She received a call on the 21.01.2020 to say the car is ready for collection and that she needs to pay R22 532.85.THIS IS OBSURD !!!.We then went to see the service manager (Gareth Pieters) to explain that the car is less than 5 months with a mileage of less than 3000km and that this should be still be covered by the warranty .He said the clutch is not under warranty and that this types of cars the clutch is sensitive, delicate and break easily????We explained to him that this information should have been disclosed to the customer upon purchasing the car and not after .We refuse to accept this amount and we will take this up further should the dealer fail to respond or take responsibility for this.She is now having to siuffer for the dealer's non disclosure of manufacturer faults.We refuse to accept this and this should be recovered under warranty !!