Vodacom

I tried to cancel my contract in May this year. It is a month to month contract but they still charged me an early cancellation fee, which was paid on 22nd of May. It is now August and they have still not cancelled my contract and they have not cut me off. I called the collections dept and the lady told me to pay the amount owed but why should I pay it when I clearly told them to cancel my contract, can someone please assist. This is showing up negatively on my credit profile.