Double billed for nearly 5 years by City Power

Unfortunately I realise this won't help as City Power don't respond or care. I've been getting double billed for 5 years from City Power and have spoken to approximately 15 different people in the time. My wife and I have both taken several days off work to spend the day at City Power in order to rectify the problem, to no avail. We've had to take out 4 different loans in order to pay the ridiculous amounts they are billing us, just so we can keep the lights on. The most recent time when my wife took a day off work for City Power, she spent the day there being sent from pillar to post and nobody could care less. 2 Weeks later all the paper was found by a bystander and had been thrown in the dustbin. We've app**** for pre-paid since we moved in and 5 years later, we're still waiting for it to be activated, despite all of our efforts and countless people we've spoken to. I really don't have any ideas anymore of who I can speak to or where I can go to get help. City Power have effectively bankrupted us and there is absolutely no recourse. Not sure what to do next.