DON'T TAKE MTN CONTRACT

I had a 2 year sim mtn card contract which ended last in March. I was instrumented by mtn consultant to give a month notice that the contract was coming to an end which I did. This month when I check my credit report I found that I have a dept with Mtn of about R1384 mind you I never receive any calls from mtn to warn me about the dept. When I call how come iam owing them it seems like my contract was not cancelled when I gave notice. It was later cancelled after I have accumulated this dept. It took me more an hour calling being transferred to different people who were unable to help or explain how did I accumulate this dept since I called on time to cancel the dept. I still don't have help I was told they are escalating the matter to the relevant people. At that time my credit report is ruined. Since they left me with this reference number: ***