Probably better to start Small Claims Court proceedings. Sharp might have someone working to activate the desired feature, but that's not sure.
If you hold a product too long, that's used against you. In addition, money in the hand gives you free choice to purchase another product.
In addition, the store has a better chance of selling the product while it's new, and electronic products don't remain new for long. The store can offer the product at a discount if necessary to move it.
Note that the store won't fight about it, but you must file a claim against the dealer. The dealer might have a program with Sharp, but that's not your concern.
Both American and Australian court systems originate from English Common Law, and the general rule is that the customer has right to satisfactory purchase. If the customer is not happy, the seller has duty to return the money.
Sorry things did not work out in a happy manner for you, for your seller, and for Sharp.