Notice of cancellation of contracts

I have two contracts that expire on 25-08-2015. All I want to do is to give notice to terminate these contracts and to convert them to prepaid. No use in phoning 084143, the number does not exist. Also no use to phone 140. It is either busy or they keep on terminating the call. Your local branch insists that I call the above numbers.<br> <br> Please cancel my two contracts wef of 25-08-2015 and convert to prepaid.<br> <br> Thank you.