MTN HORRIBLE CUSTOMER SERVICE_MTN Failing to Bill Correctly and Listing me with the credit bureau instead

With this case still not resolved, MTN has decided to list me with the credit bureau as they have handed me (failed account) to Credit Solutions Services (css), and css is constantly phoning me to tell me about the payment of R2800 that I need to make. When MTN billed me wrongly from the first month, I went to their branch to complain and they never corrected their billing. They continued with wrong billing until I handed their device and simcard back on the third month due to dissatisfaction. I mailed my complaints and they were never resolved until I gave up and wrote to Hellopeter. MTN as a non-caring business never even bothered to reply to my Hellopeter review or any of the e-mails I sent. MTN has now decided to do the opposite of good customer service to resolve my complaints against them ,and has listed me with the credit bureau instead. Can someone from MTN head office please come to my rescue?