Incorrect billing after numerous cancellation requests

I cancelled my account on the 22nd of March 2017. Telkom however continued to bill me for this account. I then cancelled this again on the 1st of June 2017. Telkom then stopped billing me for this. On the 16th of February in 2018 I received and SMS from Hugo and Ngwenya Attorneys claiming that my account has been handed over to them for an overdue payment of R3502.17, which makes no sense considering the monthly amount that I was being billed. When I called the Telkom helpline they informed me that only one of my accounts was closed when the cancellation email and form clearly stated that all accounts should be cancelled and closed. I find this extremely bizzare as this is now a year after my original cancellation and is now going to ruin my credit rating. This is simply unacceptable and ********* business conduct. The helpline call center agents are uninformed and not empowered to answer any of my laymen questions. This is frustrating and a genuine waste of my time and effort. Telkom, can you urgently intervene!!!