Finished paying the car but there's a new installments dew end of the month

My car was a write off and the Insurance finally paid their part, I then requested a shortfall letter and paid all the amount outstanding. To my surprise I have received invoice for the next installment of the same car I have paid off. They want the same documents every time I speak to one of them. Now with this new invoice and payments made by me and my insurance I asked them why do I still have installment due, No one has the ***** to return my emails. To this day no one has explained how come I must pay installment on a car that is paid off. I expected better from Wesbank I am so disappointed and angry as this is a sad chapter of my life that I would like closed real quick!