Over charging and getting away with it!

For the past 3 months we have been paying more than 2k (R2 000) per month. Our bill jumped from less than a 1k (R1 000) to 2k+ (R2 000+) per month. These people are over charging us and they always get away with this. This is highly unacceptable. I even tried to inquire with prepaid electricity, still they will need 15% for our electricity usage. I am really not coping having to pay this much every month. Where can we seek help because this is just too much!!!