Contract cancelled / charged for full month!!!!!

I received confirmation from Vodacom on 7 July 2015 that my contract which expires on 11 September 2015 will be cancelled on 11 September as per my request. On 11 September at 8AM my service was disabled.<br> <br> SURPRISE, SURPRISE!!! At the end of September I was charged for the FULL month of September and upon querying this with Vodacom on numerous platforms I was told, Sorry Sucker, we run our billing on 3 September so you just have to suck it up and pay for a full month even if you did not receive a service for a full month!! Your problem, you chose to go with Vodacom, suck it up and PAY! <br> <br> I REFUSE!!! You already went and changed my contract terms & conditions IN THE MIDDLE OF A CONTRACT and now you want to charge me for a service not received!! There is no way in hell that I will be *****ed over by Vodacom any longer and if you respond to me with a consultant will call you then I will lose it!! Answer my question as per Twitter, Customer care via e-mail AND my discussion with your *********** call centre - HOW CAN YOU CHARGE ME FOR A FULL MONTH, when my service was promptly disabled on 11 September but not have the common sense to NOT charge me after 11 September??