Cell c has zero service!

I had a contract which was canceled upon expiry. All outstanding moneys have been paid. I have proof of all correspondence and payment as well as confirmation of cancelation. Yet my credit profile shows an arrear amount. Upon contacting them 2 weeks ago when I became aware of this, I have not received any resolution despite promises that I would be contacted within 2 business days. When I try phone, I have to hang on for 15 minutes plus without anyone answering the phone. Contacted them on social media and they still don't give a damn about fixing their mistakes. Cell c will never see my business again.