Exploitation by CellC

For the 2nd month now, cellc has added an amount of R170 extra on my contract. I'm having the same fight like last month and they telling stories about "content services" which I don't even know of. I have been using this data sim same way since last year April and never had this thing but now they are finding a way to exploit me as I never finish my data. I won't afford this extra amounts and nobody at cellc seems to care of explain this or fix my account