Poor service

On 25 January 2022 my wife took a car to this company for service at a kilometre reading of 54373. The next service was supposed to be at kilometre reading of 69373. At kilometre reading of 63375 the car had problems so she went to this garage and it was found that the problem was with spark plugs. The problem was fixed and she was charged R2402 -63 which is wrong firstly because the car is still under Motorplan. and secondly because this problem falls within the quarantee of the service done on 25 January 2022 which is valid until the car reaches kilometre reading of 69373. The reason for this charge was not explained. Their service in general is also not satisfactory because the car has been giving many other problems and has been taken back several times even though it has never missed a service. Regards Mongale. M. F