No Response on billing queries.

I received an invoice charging me for electricity however we are on prepaid. I have logged a query with their finance/credit department however i have not received any feedback and now i have received the following months invoice as well, with the same mistakes and queries. Your water tariffs are all different, although they are consuming the same. Why do i have 3 readings for one month? at different tariffs. Does not make sense. The previous people who managed our water and electricity was better layed out and more cost effective.