Unhappy client

I bought a vehicle from the Springfield branch in Durban but when making the payment , my wife paid an extra amount , I then collected the car and requested for that extra amount to be credited back to me , it's been over a month now and everytime I try too phone the sales person he says he's going to send the finance people an e mail , and when I phone the finance people they say I must phone the sales person who helped me with the car , to make things worse when I go onto the website to check on my account ,it's still asking me to make the payment for the same vehicle that I've collected and it also shows the extra amount that I've paid for this vehicle.