Standard Bank Vehicle finance

I bought a vehicle from Standard Bank in 2013 and have been paying my account, but I have fallen behind with payments on my vehicle and then arranged with standard Bank to catch up my vehicle payments, just to be told that the contract that I entered into has been cancelled and that the vehicle was going to be collected, but then after long discussion, was able to keep the vehicle and as long as I pay it, I can keep it, but must understand that the vehicle is not on the contract anymore, but I must still make payments every month to Standard Bank, but given as it may, they came back to me and said that there were fees incurred and I had to pay an extra amount, if not will again loose the vehicle, but again payed what they said I must pay, until now when the vehicle is close to the end of been paid off, and this according to their statement which says that I only owe R 10743,04 so I firstly email them to give us a settlement price, which we did not get any response, and decided to phone them and spoke to a lady with the name of Avril at Standard Bank Vehicle finance, which she then submits us with a letter with a settlement price of R 14570.96 so I phoned her and asked her to explain this to me, which she then says that there is accumulated interest that has to be paid, so I asked why is that amount not on the statement or then the statement stating that I owe R 14570.96 after every month that when I pay, it gives me an amount that is owed. I cannot understand why that amount is not on the statement, then I said that they do have a hidden amount which I could pay even more after the R 14570.96 has been paid. I admit that yes I have fallen behind with the vehicle but have caught up all the amounts that they said I owed, and also the vehicle was bought on a 72 month contract and according to me it is nearly paid off, as to their statement 59 months, I imagine that Standard Bank is doing this to their customers and must be making a fortune on these hidden amounts, so where to now, I would like to settle this amount, or keep on paying till one day they maybe say I have finished paying the car off.