Cell C harassment after their mistake

About a year ago I called cell c to move my contracts to prepaid, after my debit order bounced. I explained I was not working and need to move to prepaid and cancel the debit order. They continued to debit my account every 3 days resulting in a heavy minus in my bank account from the failed debit fees. Then they only moved one contract to prepaid and cut the other two lines for non payment. I called in again when I had money and paid in the money I owed plus fees for missed debits, I did this because I needed the two lines opened they were unable to make or receive calls. After paying they again only moved one line to prepaid and cut the other one. I couldn’t pay again for something that was not my fault. This is cell c’s mistake, not once but twice. I spoke to so many people at the call centre, turns out they all just contracted to cell c and no one was able to help me. Spoke to the call centre manager as well. Now I have been handed over and receive calls daily and have it listed as non payment on my credit profile. This was cell c’s mistake and no one is able to help because there is no direct communication with cell c. Please fix your mess