Standard Bank Vehicle Finance - No help

I financed my vehicle through Standard Bank. For the past two month, they have not debited my account, which they always have. I app**** for a lower repayment in December which was approved. Since then, no debit order has gone off. I especially phoned to sort this out and find out why, and all of a sudden, all my security answers are incorrect! My account is not debited according to their records, I have to make a payment to their account every month! I was NEVER informed of this. I told the lady that's fine, I will deposit the amount, but she just kept on talking and not listening to me. I am very upset. I want to give them their money but seems they don't want it.