Really bad customer service & borderline thievery

On 25 Jan 2020 MTN incorrectly debited an amount of roughly R14,500 from my account. I then immediately logged a query to have this amount refunded. Every time I contact MTN I am told that my query is with their banking department and that my refund will be processed soon. It is now almost 4 months later and I still haven't received my refund.