Pathetic service and waiting for my refund

Mtn took an additional R580 from my account last month and when I phoned they told me they will refund me my money. To date I’m still waiting for my refund, when I phoned a week ago they told me they made a decision to credit my account with that money and on top of that they are still going to debit my account this month. I didn’t not give them permission to credit my account. I told them I want my refund and I’m still waiting. Is it not enough that their signal is **** now they also go and ***** monies from customers.