Not Cancelling Contract n Debiting acc after Expir

My 8ta contract expired on 2nd august 2015. (Contract number:+***). I filled and emailed the cancellation forms to them in July 2015. After they received my email They called me to confirm if i wana cancel. I said yes ... but they havent done the cancellation yet n are telkom mobile is still debiting my account. Iv logged numerous complaints n called the call centre numerous times to ask n enquire but they said we have emailed the back office and they will contact you. Till now nothiny has happened. N im paying for the POOR NETWORK Everymonth. Telkoms reception is really bad n i want this contract to end now im so tired of it. Please help me to cancel my contract.