Cancellation

I am very upset as in April I called the customer care service to cancel my contract a month in advance I spoke to a lady I didn't get her name which I regret. She told me that it is not necessary to call a month in advance if I want the number to be still active only if I was not going to use the number at all the I call a month in advance. I said o ok that is nice but according to my knowledge I must call a month in advanced so I left it and I called the day my contract expired 11 May 2015 spoke to another lady she cancelled it. I phoned MTN Highveld mall as I can't get through to the call centre just to find out I must pay R600 and something. I will NOT pay this as the first lady told me I only need to call in the day my contract expires. I would like I record of what was said I am sure u guys have copies. The number in question is ***. The number you can call me on is *** I am angry I will not leave this here!!The ref no i was given is ***. now i must pay another month i will not pay this and its said there is charges on that number but i dont use it so how can there be charges!!!