Qantas Classic Rewards – Can I cancel return or one leg of a rewards flight?

Recently due to some travel changes, I had to book a different return flight with another carrier due to no availability on Qantas Rewards Flights.

Online it only gave me the option to cancel the whole return flight not change to just remove one leg of a return flight

I called up Qantas Customer services and they were about to cancel just a single leg of my flight and keep the initial flight