Negligence and worst service

I called the contract cancellation department on the 27th of July 2015 the cancellation was done by the lady i spoke to, i was told that i need to switch my phone off for the entire day on the 31st of July and switch it back on, on the 1st of August and it will be prepaid and no longer a contract.<br> <br> I received a sms stating that my account is in arrears and when i called the same department today 13th August 2015 to inquire about this i was told that the cancellation done on the 27th wasn't successful and i need to pay the outstanding amount for this month and then do a cancellation, this is clearly a fault and issue from Vodacom and they should rectify their mistake and not want me to pay for a mistake they made.