Cannot understand the serious lack of service.

I am so disappointed by the level of service I've been receiving from Telkom. My account was in arrears for a short bit but I managed to pay off my entire contract amount and then struggled to get through to them on the via, via chat, via their email service and Facebook to cancel my contract. After sending all the details via Facebook to institute the cancellation I received a statement showing that there was no amount outstanding, so I assumed my account was successfully closed. Now I receive a statement with a bill of over R900 showing a failed debit order on my account in April. They are now very quick to send me emails and phone me about upgrading this account when it should have been cancelled a month ago. I am fed up and refuse to pay the amount outstanding, made reasonable attempt to contact Telkom to close this account, therefore I do not accept your latest statement. I want someone to contact me about my latest statement and my conversation with your social media team about closing this account, I have records proving my request. Furthermore they make it so difficult to pay your account and you constantly get sent from pillar to post between calling and dealing with them online and dealing with store staff. I have had enough!