Telkom refusing to send me a letter to clear my credit report

Someone without my consent opened a mobile account with my details and only found out when an installment of R25K went from my account which I was able to reverse it and was informed I owed telkom R13 991,00. I opened a case with telkom which was successful in my favor but I was amazed to find that under my ITC I had a default if R13 991,00 from Telkom. I called telkom and was promised that a letter will be sent to trans union to update my credit report and which was not done and telkom does not want to email me a letter showing that account has been settled off and this back and forth has been happening since beginning of the year and now my report is affected and telkom does not want to help, please help