Change contract to prepaid

I phoned MTN on 19 April 2016 to change my contract to prepaid. Somehow somebody marked my account as a business account where I am an individual. I left an email and phoned again 0n 21 April. I have been on the phone for more than 15 minutes without any help. <br> <br> This is nonsense. <br> <br> All I want to do is cancel my contract and that proves to be almost impossible.