Misrepresentation in order to sell a product.

I was phoned by the CellC agent to do an upgrade. I explained that I do not want to pay extra. So I was told that I will be paying the same money I am already paying. But now I was billed for +- R700. I phoned CellC and they told me that I have open lines. I asked them to close the lines. And in December I left sufficient money of +- R450. To my surprise I was billed +- R820. Which was returned as unpaid due to insufficient funds. I phoned again and spoke to an arrogant guy who spoke to me very rudely. I have been taking out CellC contracts and has had prepaid accounts for more than 10 years. For the relationship with CellC to be destroyed like this. I do not understand why I should pay +-R1600 for Cellular phones now end of January. I was adamant that I want to pay the same amount. I was not told that this is an open line. And when I found out still the lines where not closed. I am very disappointed.