Unpleasant. Air France and Qantas are not even in the same airline alliance (AF Skyteam and Qantas OneWorld). I would avoid such combinations and if codeshare only between airlines which belong to the same alliance. The Air France Qantas codeshare agreement was started in 2018 and who knows how well both airlines are integrated. Anyways since it is an official partnership Air France is your's to talk to in case of changes even if the Qantas flight is changed. As soon as you are in SIN / PER I would assume Qantas takes over the customer service for Air France.