Mtn Legal nonexistent

I have been trying to get a hold of MTN Legal and settle my debt with the company, no phone call back neither have they explained to me what the actual debt that I owe them is for. I cancelled my contract with them in April 2017 but I still seem to be owing even though I paid what I owed in the cancellation letter they sent me. This is really bad service considering that I have paid what I was owing, and that I am even willing to pay what they say I owe even though this amount is generated after the contract was cancelled and closed. I would just like to get a clear credit rating again but the call centre cant help and they keep on giving me reference number after reference number but still no reply as to where I should pay and how much.