Car cancelation contract

I bought a car on the 14 of December 2023 at Pretoria menlyn I discovered the car was in a very bad condition and shaking as I was driving it on the very same I took the car back to the dealership and it was checked and they also witnessed is faulty I was not happy at all and I told them I no longer trust them and asked them to cancel the contract and gave them their car back now they want me to pay for the car I returned back the very same day.. How is that possible