ABSA Prosperity Refund - no luck

I received a sms and letter from ABSA 25 April 2019. The letter informed me that my warranty policy was not lapsed on the expiration of the two year term and that they have to refund me R 651. They asked in the letter that I confirm my banking details. I have stopped counting the amount of hours I have spent on the phone with ABSA. My lunch break is 30 minutes and every time I phone I spend more than my lunch break on the phone with them. They keep telling me I must speak to a different department. They transfer your calls from one department to the other. Every time I speak to a new person I must give my credentials like ID number etc AGAIN. They told me they have 7 days to refund me. Today is 27 May and I still have no refund. It is impossible to get anywhere with them on the phone. Who can tell me what else I can do?