Miscalculation of my loan interest 😏😏

They finally went through the process of selling the car and allowed the dealership to settle the amount agreed on.But now they calculated the interest rate from the original price of the car instead of calculating it from the shortfall since it is my original total amount of loan now.The amount they calculated the interest from is the original price of the car not even the settlement.They must take a closer look on the calculation terrifs and fix the mistake unless their interest rate of a loan is 50% which is impossible.They say the Total amount of my loan is R363 107.50 which is the original cost of the car, while R245 000 of that amount is paid already.My shortfall is R115 703.33 since my settlement is R360 703.33.The R115 703.33 shortfall is now my original amount of loan or the total amount of loan since the car has been sold,then from there they should calculate their interest and determine the outstanding amount.