Vodacom - day light *******

I cancelled my contract well before the 30 notice period. Firstly it was so difficult as Vodacom insisted I go on prepaid for R65 a month. Eventually they got the message that I just want to cancel my contract. I received a confirmation of the cancellation. I was converted to prepaid today (as I requested), yet I am being charged for a whole month on contract. When I ask the agents why, they just reply sorry for the inconvenience but I must pay for the entire month. I cannot use the phone for the remaining month as I am now on pay as you go but yet they are charging me. I am so happy I have cancelled with them as this is day light *******. Vodacom is tanking my money and not providing a service in return. I am disgusted and appalled by the service!