R6,000 bill on a top-up account!

<br> I have been using a Vodacom simcard (number ***) in a modem to connect to the internet. This number has always been on a TOP-UP contract. So it was a great shock when Vodacom confronted me with an account in access of R1,000, which is impossible with a TOP-UP account. Subsequent enquiries showed that Vodacom has unilaterally switched by account from a TOP-UP to an ORDINARY account. I challenged this, but the consultant was adamant. She indicated that she would switch the account back to a Top-Up. To my horror, the next month, Vodacom presented me with an account of almost R6,000. They dispute that this contract has ever been a top-up account. I authorized them to retrieve the original contract. After umpteen times of wading through the bramble bush which is Vodacom's help desk, I still can't get them to provide the original contract or my authorization to change the contract to a Top-Up account. I know I have never given such authorization.