Poor Service and Attitude

I have been calling and emailing Telkom's billing department, creditors department and their supervisors since the 04/02/2019 trying to get a a clearance letter due to their stuff up (I have also emailed their complaints department with no response). They continued invoicing an account that had been cancelled since the beginning of last year and now the account holder has been blacklisted due to non-payment and requires the letter to send to the credit bureau. I keep getting promised that I will receive the letter by the end of the day or that a supervisor will call me back to assist me, none of which has happened. I have received absolutely no feedback and their call centres' only solution for me is to email them again. This is frightfully poor service and attitude I have received from Telkom.