MTN is ***, you have been warned

So I had a contract with MTN which expired 3 years ago. Just yesterday I went instore for a new contract, to my surprise they told me my account is with their legal department. Upon hearing this, I phoned MTN who told me that I owe them R4500

Enquiring further, they said my contract has been running for over three years (after the settlement) because it was not canceled. Turns out they have been billing me all this time for a number that is now prepaid. What for, I ask, because it's for services I have not been using since its now prepaid.

Who do I escalate this too, ICASA or Consumer Protection?

This is ***** !!!!!!