Telkom
Billing on prepaid listed on credit burea

I had prepaid phone for almost 7yrs. 2012/12/01 my telkom line was changed to normal line and i was not informed about it . early jan received a statement being billed R 350.00 for the charges that i was not aware of when i called in they told me it was a fault it will be sorted out immediately. Now in April im listed for that amount i' ve called the contact centre spoke to several consultant no one is willing to assist. i need a prove that shows i did agree for telkom to convert my line to normal line. I need my name to be removed from credit burea NOW...