Refund - still waiting almost 3 weeks

So it has been more than a month since Cell C has debited my account with R3000 double the amount of my monthly payment on the last month of my contract. I have asked them to reverse the amount and pay me my money. I have called in more than 12 times. They texted me more than 10 working days that they will send my refund. I am still waiting. The number is question is ***