Poor account maintenace

I gave instruction to close my account on 12/12/2016, again on 13/02/2017 and finally on 20/03/2017 for the effective date of 31/01/ 2017. This is more that 30 days notice as per their requirements. I account was paid in full and in time until 31/01/2017. Telkom only closed the account on 3/05/2017 and passed a credit until 28/03/2018. After numerous attempts to get it resolved a further credit was supp**** but not until 31/01/2017. The account should have been closed on 31/01/2017 as I gave sufficient notice. They have blacklisted me and I'm being harassed by the creditors MBD for these ********** claims. They have on record that the line was used once during this time, this is not for my account as Telkom did not close the account on the agreed date. I have even paid for the extra 2 months that was ********** charged but still I was blacklisted **********ly and MBD is ********** claiming fees.