Unfairly listed as a bad payer

Vodacom renewed my contract without my consent. I later found out I owe and paid the amount and they didn't update on credit bureau. Whenever I call them they say I do not owe them and they will issue a letter confirming that. I am struggling to get to legal department to obtain such letter and the attitude from consultants some just hang up instead of assisting or else transfer me to the customer service dept. This matter has got nothing to do with customer services. I do not know what to do now in order to obtain this letter from Vodacom. Every time they say they are escalating the matter, however they cant give me the contact details for the department where the matter is said to be escalated to. I will never do any business with Vodacom. I even spent time to seek held directly at Vodacom Northgate 3 times, no one could assist except to say shame. Its time to cut all ties with Vodacom. Even if I get a letter I doubt they will consider refunding the money that they ripped me off as I never used any service I had to pay for.