It doesn't matter what the dealer says, or whether or not there is a warranty, you have a statutory right to get what you paid for under the Trade Practices Act 1974. If the item was faulty, it is a breach of contract between buyer & seller and the buyer is entitled to remedy from the seller - including full refund (not just store credit). If it doesn't last the period of time you would expect from the kind of item you purchased, you are also entitled to remedy - in this case replacement or repair. It is the seller, not the manufacturer, who you have the contract with, and is therefore the one obligated to act.
It is illegal for a store owner to mislead customers by implying you do not have these rights. "The ACCC treats misleading conduct very seriously, and can take court action against businesses that mislead or deceive consumers about their rights. This can result in fines of up to $1.1 million for businesses and $220 000 for individuals." Warranties & Refunds, A guide for consumers and business, ACCC 2009.
