CONTRACT UPGRADED WITHOUT MY CONSENT

My cell phone contract expired in July and MTN called me about an upgrade but i did not agree to anything. In August i was billed with R195 for MTN top-up 100 contract that i did not sign up for. I called the *** number to query the transaction and I asked for the contract to be cancelled and i was told that i would lose my data (1GB) and airtime. This happened and I thought the contract had been cancelled. To my surprise I still have a contract with MTN and it expires in 2017. Please switch my number *** to prepaid and cancel that MTN top up 100.