Still being charged after contract terminated

Knowing that my Cell C contract expires on 7th of Oct 2015.I went to the CellC office in Rustenburg in Sep. One of the store agents gave me a card with the no 084 143. On 5th of Oct I called the above no. A lady by the name Zukiswe told me that I must call at the end of Oct. I specifically told her that this call must be taken as my notice. I called the no to cancel my contract and change it to prepaid. Then I was told that the contract will only be terminated on 2nd Dec. I was really disappointed as I needed my contract terminated immediately. <br> <br> Finally after my contract was terminated on Dec 2nd, I received several higher than normal charges, even though the phone was being used only as a prepaid. I was charged R1231 on Dec 1st and R747 on January 1st, even though my normal contract was between R400-R600. Surely I wasn't charged R747 for 1 day (Dec 1st)??!! Especially, as I had called to cancel the contract at the beginning of October and it wasn't done so immediately due to Cell C's delays. And R1231 is 3X my normal bill. I am very unhappy about slow response time to cancel, no response to a complaint sent Nov 2nd and am receiving extra high bills even after canceling.