Can most definitely be done. My OWA just got ticketed last night, almost all business class but one economy and one premium economy flight in there too.
From the first phone call to the last was a 48 hour period. In that time I spent 20 hours on hold or speaking with them. First problem was it not capping out the points, even though the route was within the rules (as evident by it being ticketed eventually). Second problem they couldn't calculate the taxes. Third problem was a payment issue on their end, I think maybe they had to redo the taxes but kept saying payment issue. Refused to get off hold until it was sorted but they would come up with excuses to get me off the line. Made maybe ten calls in total.
Anyway all done now, absolutely exhausting experience, I won't be back to Qantas for anything that can't be booked via the website.
Total taxes for the below trip was around AU$1200 per passenger for reference for anyone.