Poor customer service from Absa

I bought a car of which I was financed by Absa and I wanted to change the deduction date as my salary date has changed and I went to the branch of which they gave me the phone to call the tvehicle finance department and the lady l talked to told me that if I change the date my installment is going to increase, I tried to explain to her that I am not changing anything iits only the debit order date but she insisted that my installment is going to increase and I told her to forget it and the lady was so rude