cancellation of a contract

i have had a phone on telkom and wished to change it to prepaid, i sent through the cancellation on 2 occassions as telkom doesnt respond to emails i also had to phone in my self in order to get it switched to prepaid as telkom did not do so when needed. i also noticed i have been billed an extra amount for data since december, this wasnt part of my contract and have since queried the extra amount which has been escalated and has case number ***6, i have not heard any feed back and the department i need cant be called or emailed. service at this point is beyond ridiculous.