As you plan to refund your ticket a few hours before departure, be aware that you must to it at least 3 hours prior to departure to avoid the No Show fee.
And also pray that there's not technical issue preventing you from asking the refund 3 hours prior to the flight.
Personaly, I would plan to ask the refund at least the day before departure, so I still have time to call QR in case I have a problem with their website.