Inconsistent Bills Not Corresponding To Usage

I moved in to my unit on 1 December 2013, and was welcomed so warmly with a NetVendor brochure explaining exactly how I would be billed on a weekly basis for my prepaid Hot Water usage. The last 18 months have been hell for me forced to fork out money I don't have for inconsistent hot water bills including bills for months i was not even in the unit (0 hot water usage but bill says I used 14202kL), dealing with NetVendor and their call centre which can never answer my questions and i end up being passed around from person to person. It has been 18 months, and still, this continues. They ONLY respond to what they want to respond to and simply ignore you if they can't answer you or cant explain aspects of their system, service and inconsistencies in figures they have billed you on. Are they listed? Are they certified to carry out the service they do? Why am i not getting the service they promised in their brochures? I have highlighted all these inconstitencies with them, including the CEOs of the company are ccd on my mails, but still, NO RESPONSES to my questions. If I don't get responses, I will be taking further action incl. media to expose how they operate & deal with customers.