Refund delayed

I paid my subscription more by mistake on the 28-07-2020. On the 30-07-2020 I called MTN call center and one of their agents opened the ticket so I can be refunded, she asked me to send proof of payment, which I did. I also sent it to their customer care. It's 2 weeks now and nothing is happening. I need to use the money, now I'm stuck. When I called today to find out what is happening, the agent told their still waiting. I see that they don't care, but when you the client ows them, they quickly suspend your account and call you every day for you to make payment or be taken to Credit bureau.