Generally if you realised your error within a day or so, it is then more likely that you did make a genuine mistake and QR *may* make that exception. But generally from experience, QR is not at all that forgiving and they stick by the rules to the "T".
Do people go to Australia for 5 days? Well, if FT is anything to go by, yes they do.
You do have to contact QR in one way or another, and tell them that you'd like to buy up to the next fare level, which will give you some flexibility. The next best fare is HLEE3MGB fare basis.
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Yes its great to buy this thru online, but always make sure you check exactly what you did cos there's no turning back. If you made the booking on the phone, at least you might hear the mistake when the itinerary is read back to you.
Sorry, but it might look like you're out of luck.
FYI - QR 5 star airline is usually refers to the inflight service. But their ground service (ticketing, customer relations, and even airport ticketing (which is non existence in Dubai by the way) is about a 0.5 star.