At this point, you'll need to consult consumer protection policies in Indonesia. Every country's consumer protection laws are slightly different and there are typically many ways in which a given retailer can legally operate under those laws.
Here in the United States, you can probably try several things before launching into legal action. You can bring it up with the merchant in question; if they have a customer satisfaction policy, they will typically follow their policy.
Another option is to use the merchant dispute service from the credit card company if you make the purchase with a decent credit card. They will act on your behalf in discussing the issue with the offending merchant. American Express is the very best at this, and I typically make all big ticket purchases using my American Express card (as well as major travel arrangements like airplane tickets, hotel reservations, rental car reservations, etc.).
Few instances will make it to court, but there is always an option to file a legal action against the merchant. Most merchants won't let a situation get this far.
Again, my comments are based on US consumer protection policies, particularly those for a California resident. I am not familiar with Indonesian consumer protection law.
Good luck.