Letter of demand ages after cancelling landline

I cancelled a landline more than a year ago by going into the Telkom Customer Shop at Menlyn. When I cancelled the account the account was in a credit. Telkom owed me money. I never got anything from Telkom telling me that I still owe them any money. I received months after I cancelled the landline a phone call from Telkom telling me that the line was now cancelled. On 08-01-2016 I got a letter of demand regarding outstanding telephone account dated 27 October 2015 in my postal box. I phoned 10210. They told me that my account was suspended and if I pay it will be re instated within 48 hours. I told them I cancelled the phone and do not want it re instated. They also had the wrong tel nr and email for me on their system. They gave me a number to call the debt collectors for Telkom.. On 11-01-2016 I went to the Telkom shop in Menlyn and got a reference number and sms that told me that somebody from Telkom will phone me within the next 2 hours. It is now 3 hours later and nobody phoned me. I also phoned the number of the debt collecters given to me by the operator at 10210. They told me that they are not doing any more work for Telkom and that I need to contact Telkom