They might within days of the flight. I flew QR once and that is how I did it. I had a PY ticket to DOH with BA. Week before the flight QR J opened up directly from YUL and made the change fro $ 58 CAD.

Or you may get an offer online that you can decide whether it's reasonable.

Airport upgrades tend to be expensive. When I was traveling I was curious and asked. The going rate out of YUL was something like $ 2400 CAD. Too much for me!