Cancelling One Leg of Classic Rewards Return Flight

Hi All,

Last year I booked an economy return flight from 3 Feb returning 22 Feb Melb -> Tokyo (Narita) and Tokyo (Narita) -> Melb on QF79.

For this return trip total I paid 120,000 points + 300 bucks on top.

Just today I FOMO purchased a business class one way Melb -> Tokyo (Narita) on the same plane as my departing leg after seeing it on seats.aero for 98,000 plus 300.

I have called qantas to request the first leg is cancelled or at least partially refunded without cancelling the entire return economy booking. This was denied by two different support people quoting something like "classic rewards is a deal offered only when leaving australia or new zealand."

I cannot reasonably cancel this flight and rebook with qantas as rewards seats are gone and I would have to pay $2250 for ONE WAY. I made this clear that I would be forced to go to another airline and they were indifferent, i requested escalation to a manager and i was told the result would be no different.

Has anyone else dealt with something similar, and is there a way to get this booking split?

Worst case scenario I would have to cancel both economy flights and take a one-way economy flight with thai airways or jetstar instead, but Ideally, i'd like to cancel this departing leg by itself.

Hoping you all have some words of wisdom to share.

Thanks :)