Unauthorised increased contract value

I have had a Cell C Data Contract for the last 2 years - R155.35 for 15GIGS of Data. I spoke to a consultant at Cell C about two months go when I called in about rectifying my debit order which was returned unpaid. In this conversation I asked the lady what would happen to my contract once the 2 years is over, and she said my contract would automatically change to a 'month to month contract' and that I did not have to call in to ensure that this would happen as it would automatically change and the costs will remain the same as would the amount of data that I received. But contrary to that I have now been billed an amount of R302.46 - DOUBLE MY USUAL CHARGE, what's worse is they have now run a debit order to that value of my account, WITHOUT MY CONSENT ! And even worse than that is that I am currently not receiving a full salary as I work in the Tourism & hospitality sector and we are not fully operational as yet. So I phoned the Cell C customer services last week and spoke to a consultant who could tell me nothing more than she will escalate the matter and I will receive feedback within 48 hours. I agreed to her escalating the matter and waited for a response but when I didn't receive any feedback by Thursday this week, I called in again. I spoke to a different consultant this time, Nokwazi. First I had to spend time explaining to her that my account was up to date in terms of payment, which she would clearly see from the invoice she was looking at. Then she kept telling me that they were recovering the outstanding amount & my monthly instalment - which is completely incorrect cause there is no amount outstanding except for the current months charges. And the invoice she was looking at clearly reflects the billing charge being for my package only with no extra invoice lines. After repeating the reason I called about 5 times, she finally said she would escalate the matter as there was no record of the matter being escalated by the previous consultant, not even a note that I had called in. So I agreed to that, she at least gave me a case number - *** Then in the meantime, yesterday I received my June invoice from Cell C and it's for the amount of R301.62. I am actually so annoyed, I want to cancel my contract!!