Continued billing for account closed !!!

I had a landline and ADSL with Telkom. I went to the Lakeside mall branch to apply for a cellphone contract which offered unlimited phone calls and data on cellphone . Great deal R999.00 excl VAT per month. I cancelled my ADSL and landline . I kept getting SMS messages I need to pay +-R360.00 .I called to query it and was assured on numerous occasions by the call center that the message must have been sent in error and to ignore it as according to their records I don't owe them money. Months later I get a call from a credit company saying I will be handed over to the credit bureau if I don't pay the outstanding amount . Which by now had accumulated to R+-1000.00 I called Telkom and was told to first close the account as they have no records of the account being closed and they would sort out the error .I again via Email closed the account and didn't hear a word for months till recently a credit company called again demanding+- R3000.00 to be payed immediately or I would be handed over to the credit bureau. I cannot find any reference numbers as the email account i used is now obsolete. I am at my wits end ! It is very distressing . I refuse to pay for their incompetence . I would love to sue them for the stress caused and time wasted trying to sort out their problem. Surely they can check their "recorded" phone messages to see that I have been misinformed by their staff ! Had I known earlier I could have sorted it out . I was assured by call center that it was an error !