Poor Showing Standard Bank VAF

I have been a long time customer of Standard Bank and I have been going through some difficult times financially and got behind on my car payments. I had missed a previous payment arrangement but was getting a bonus at work so called Standard Bank to get my account up to date. I spoke to an agent Stanley S. Maganya. When he set up the payment plan he made a mistake with the calculations and my account was debited by nearly R1000 more than what I owed. He owned up to his mistake and said he would refund me on Monday. This was nearly 2 weeks ago. He does not respond to my emails. Won't give me a date as to when I will get my money back and my attempts to escalate the matter have been ignored. Amazing how on you they are when you owe them money but when they owe you money they feel entitled to take as long as they like.