I only had to do it once years ago when an addon company charged me twice for a product and wouldn't respond to my inquiries. I called my bank and explained the situation and after they attempted to contact the company on my behalf with no response after two days, they credited my account (removed the second charge) and everything was fine.
In this case, assuming you payed with a credit or debit card, I suggest calling your bank and explaining the situation, emphasizing that you did not receive the product you paid for, and have been unsuccessful in trying to get support after # attempts. Now, I'm in the US so this may not apply at all for New Zealand, but it's worth investigating as soon as possible.
http://en.wikipedia.org/wiki/Chargeback