You could have been mis-sold for any of the following reasons:
You were not made aware that the broker / dealer would be paid commission by the lender
You were  not made aware of the amount of commission paid to the dealer / broker
You were was not made properly aware that you would not own the vehicle at the end of the contract
You were not made aware that you would still owe a significant amount to purchase the car
You were not provided with any other options in which you could purchase the car
You now believe that the interest that you paid was much higher than other options you could have had