Why isn't my contract cancelled?

I notified Autopage on 3rd June that i wanted to be shifted onto prepaid as my contract was coming to an end. They told me on the 27th July it would be effective. On the 27th July, nothing happened. I called in the call centre and they said its the 28th July at midnight. It is still not shifted to prepaid. And the call centre is useless they keep telling me the next day. What is going on?<br> I want to be shifted onto prepaid my contract is over!