Telkom and their useless accounts department

Yet again Telkom proves how useless their accounts department it, I cancelled my account in July 2018, and received confirmation of the cancellation. Months following I received invoices from Telkom, I called to query and was told by the accounts department they dont know why I am being billed and to ignore invoices as my account is cancelled on the system. Fast forward to current... I am in the process of applying for a bond and am being declined due to Telkom having listed me as a bad payer. I contacted Telkom on the 14th November requesting a letter confirming this was done in error. Waited 2wks and still no letter. I called today and was told they don't know why the letter was not sent and I need to wait a further 5 days for the letter. For someone who has paid their accounts timorously I am being penalized for Telkom's incompetency. Company's like Telkom don't realize the impact of such mismanagement of their accounts have on peoples likes.