Unauthorised billing by telkom mobile

I completed a Request for Contract & Service Cancellation form as advised by a Telkom mobile consultant. On the form I specified that I do not wish to renew the contract and I want my sim card to be converted to prepaid. I emailed the form on the 26th of march 2015 and specified both in the email and the form that I want the sim card to be converted to prepaid. But for some reason Telkom kept my sim card on contract. The email address specified on the form was [Email Removed]