Issues regarding warranty with Motorite

I bought a used 2012 Hyundai elentra gls car at Nellas dealership in Pretoria rd, Kempton Park,that was last year August 2021, after signing the documents i took the car ,now I having problems with the car.I called them they said I must take the car to Bosch since the car its still under warranty, now Bosch contacted their Motorite insurance to claim.Bosch diagnosed the car , they required R19 000 to fix the car, Motorite aproved R7 000 they say I must pay R12 000. , this unacceptable since the cat is under warranty.This has caused me lot of stress and i am very frustrated,i tried calling them several times with no sucesss,i have done all within my means to sort this issues out but hellopeter is my last option.