paying for something I didnt get and didn't want

Bought an celerio that they said was already fitted with a tracking device but I did not want to have it but they said the car has been fitted with the device the contract for finance was there and I thought its best to have it becuase everything was done. Then I found out there is no device fitted and the service from car track has been useless I don't want the device fitted and I want my money back! They chose that supplier and they **** about the device so they need to sort out this mess!