Handed to debt collectors without notification

I am so Gatvol with MTN. They are a company that think they can use they status to destroy peoples lives. They have made my life a living hell with their arrogant debt collectors Shabir Shaik. This is over a contract that had expired last year September 2014. I sent an email notifying MTN to cancel the contract and to let them know I wont be taking any upgrade. After a while I realized the contract was not cancelled they were still deducting my account. I called them to be told they will check the account then let me know me the outcome. Since I had not heard anything I cancelled my debit order with the bank. 3 months later I was called by debt collects claiming R1200. without any notification from MTN. There was no sms, email that was sent. Now 4 months down the line the outstanding balance has increased to double the amount. Unfortunately all this started when I was retrenched of which I told their debt collectors that but they keep insisting I must pay them. How can I pay MTN when I don't have any income. I have tried to talk to both MTN and Shabir Shaik who are very arrogant and very rude. As a loyal customer for more than 10 years I want nothing to do with MTN from now on.