Over billing and being told that it is re-billing.... WHAT?

After receiving a Tax invoice stating that my elderly parents have used R2500 more than what they have been using i went through invoices from the month of June and learned that the amount charged is based on the difference between the previous meter reading and the current meter reading. For the month of September an incorrect previous meter reading similar to that of May was used to bill my parents's account. On querying the matter i was told that they were not overcharged but re-billed for 334 days in order to cancel the estimates made over that period. WHOSE FAULT IS THAT?

This is serious injustice being done by ESKOM, I have constantly explained that they used incorrect meter reading numbers but they refuse to assist.

I am deeply frustrated and dissapointed by how they choose to patronize and ill treat their clients. Can I please be referred to a relevant individual to help. PLEASE