Contract not cancelled after requesting it.

I phoned on the 4th December 2015 to cancel the contract as I was told to phone and cancel the contract a month before the contract ended. When I was on the phone I was asked why I want to cancel the contract and I told them I want to go on prepaid and they cancelled it. I phoned again end of December 2015, beginning January 2016 to check my balance and was told my contract ended 6 January 2016. End of January I received a statement to say I owed R686. 98 so I phoned to find out why and was told I still have to pay a month to finish the contract. So I paid that amount on 8 February 2016. I received a statement today on the 15th February 2016 to say I owed R879.29 I phoned today and while waiting to speak to a consultant in the cancellation department the computerised voice said my contract ends October 2017. When I eventually got through to a consultant my call was cut. I tried to phone again a few times between 16:30 and 17:00 and when I got through to a consultant my call cut again. I then phoned on my daughter's phone which is also on the contract and I got through to a consultant which told me the cancellation department had closed and to phone again tomorrow morning.