installment going into wrong account

I purchased a 3.0 D4D a few years back for my business and the instalment was paid via debit order. My business struggled as my client was not paying and I ended up removing the debit order and paying manually for the bakkie. In 2013 I bought another vehicle financed by Wesbank and that's when things started going wrong. For some reason the money my father was depositing for the bakkie was now reflecting under the new vehicle. We were not aware until someone called to tell us they were about to repossess the car for non payment. He gave us the reference and transferred the funds into the right account. 6 months later I received another threatening call to repossess my car for non payment. I referred him to my father as he handled the payment. Same issue was at hand, the money is going in someone's account. I have since received another threatening call with the same problem but nobody fixes the problem on Wesbank side. I have decided to stop making payment as it seems my money is funding someone's instalment and my car is R80k in arrears. Wesbank is quick to call and want to repossess as if I don't want to pay for the car but the account problem is not fixed. Now I have bad credit.