Engen - Poor customer service

Good morning, I'm drafting this with great sadness as I experienced bad customer service at Engen (Penta) Mokopane yesterday on 09-04-2024. I went there asking for a refund as their machine deducted twice in my account, this incident happened on the 07-04-2024 at around 01:00 am, I waited for 3 days so the money would reflect but it never did. That's when I went back yesterday to explain what happened, their response was really rather unexpected, they made me wait for 30 minutes as they were going through the speed point to see past transactions, i eventually became impatient and told the manager that they can't make me wait close to an hour, I have somewhere to be. The manager then took my contact details and address, she then promised to have the money refund by the end of the business day but that never happened, any advice on how to handle this matter.