Billing Department refund

Good day, Please help me get my money back. Iam a postpaid customer with Mtn where iam billed R709 monthly but on the 26th of October they took R2200. I called to enquire about it where I was told Mtn billed me incorrectly due to self_service and they will fix it and return my money . back . I have been calling but all iam getting is that my query is still "open waiting for the billing department to authorise. Iam really getting irritated and angry now because it's money we talking about. It's my salary that iam supposed to live with. I want my R1330 back. I didn't subscribe to anything it's Mtn fault but they are dragging their feet (stupid Billing Department) I want my money. My no is ********** 842 Email **********