I cancelled my contract but still being billed

I spoke to Mpho Ndlovu about cancelling my cell phone contract, he gave me the amount i needed to pay, which i did on the 13 July 2015, i faxed all my proof of payments to Mpho, he did not get back to me after he assured me my contract will be cancelled. I call the useless cell c call center and not one person can help me, they can only transfer you from one department to another, like i said i have been trying to cancel this contract since June, i refuse to pay for August, as from my side i did everything i was told by Mpho. I would like someone to get back to me with a solution and not a problem,