See if you can change flights in the QR app. I’m in Singapore at the moment having flown QR on a BA 125 stock ticket - I need to come home early, tried changing flights on the Qatar website and got told no, try your travel agent of the app.

Successfully did it in there and it’s changed my ticket to a QR issue 157 stock one, with their booking rules.

There was £300 change fee and fare difference (£170) - so you’ll have to pay, but may be worth it if you can get more of your money back