Contract cancellation and billing

Vodacom is the worst network i cancelled my contract on the 1st of september since my contract was coming to an end around the 17th of september,so they had a full month which is sufficient time to cancel the contract...to my surprise the contract has'nt been cancelled and in arrears to the tune of around R 698 or something for wht whn i was paying R488.87...whn i contact their call centre i get different answers some agents say its suppose to be cancelled they dont knw why it has'nt been cancelled....nw wht i find od is why the different answers n being in arrears so quickly is it because i cancelled the contract?..m ****ing fed up with this **** network i just wish people would dump it