Please fix my credit report

I honestly never had a problem with this service provider until the time I refused to renew my contracts after 2 contracts. I am in pain as I write this because my credit score has been decreasing since last year November.

So an agent I do not know decided to open an account for me upon the end date of my old contract, I refused it but somehow they do not know that, they started debiting me along with my last debit order, I kept reversing the debit order until I decided to settle my last debit order separately through EFT but they still debited me for what I do not know, I am angry as this reflects on my credit score, I wanted to buy land and missed it because the financial provider I was attempting to get a loan from said I have not been paying Cell C. Please fix this mess I am getting so much anxiety from it because it interferes with my financial plans. I called them and they told me to get an affidavit and email it to their ***** department, I did that 13 days ago and until this damn day there has been no response. To say I am angry would be an understatement. Pleaase note that I no longer want anything to do with Cell C so I have discontinued using the number even though it was now prepaid. I am super angry with this company.