Vodacom- worst possible service provider

A few years back, my father baught me a laptop- on contract with vodacom. Part of this package, was that I receive 1 GB of data each month. Now after the laptop has been paid off, vodacom has suddenly decided (without my permission) to make my account an open account- which has left me having to pay a bill of R 2 000.00. When they were phoned, I was simply told that the account has always been an open account- a fact that is not true- and that they cannot help me. I find this absolutely unacceptable and I will definetly close my account within the next few days. I have never experienced such horrifying service and I advise anyone wanting to open an account with them not to do so.