Impact Disgusted me

I have been renting for more than a year at Impact meters. My account or bill was never more than R3000 at the most for 11 months. All of the sudden I received a bill of R3500 and now R5800 which since apparently I was in arrears reached almost R7000 including the outrageous R750 connection fee. When requesting an explanation they told me that they increased my deposit with R2350 which is totally unexceptional because I did not agree to it but still my bill is too high. This month they couldn't give me an explanation but they want to install a prepaid meter. Oh my word, how do companies still get away with things like this. I am taking this matter further. Worst part is that I have a 2 bedroom flat.