Horrible customer service for MTN South Africa

A few months ago I went to an MTN store to change my method of payment to cash because MTN advised that they cannot debit of my primary account. The MTN employee and MTN shop Brentwood Park said he had updated my payment method to cash only to find out 2 months later on my credit report that MTN says I missed 2 months of payment. When I went an enquired only to find out that the idiot who helped created a second billing account and a debit order is failing on that account. I never missed any payment and according to MTN system, my account is in good standing however, the second billing account that is not even attached to any contract shows that I am owing. I have logged a complaint with the MTN complaints department and even logged a case with the store in question and still have not received feedback after two weeks. Every time I go to the store for feedback, they take my number and promise to give me a call which they never do and the MTN complaints department have not given feedback despite their auto-response my saying that they will come back to me within 24 business hours. Maybe I don't understand what 24 business hours mean or MTN's complaints department doesn't. What do I need to do to get this resolved, should I go sit at the MTN store until they sort out my account coz this is unacceptable?