I'd keep pushing back on this. Ask the agents who deny you what the rule is you're supposedly violating. Another suggesting might be to jump on the phone and plan the exact same itinerary you've already got, but on different dates, in the hope that you'll get an agent telling you what you've planned is valid. Then ask them to look at your existing itinerary and do what you want.
At the end of the day, though, I wouldn't be losing your entire trip over a short hop between MEL and ADL.
SUCCESS! - got my last flight added.
I decided to try one more time and after again being told the the flight couldn't be added I pressed on what rule was not being complied with and initially got the response:
"It's because there are different airlines and processing change or adding another leg may cause discrepancies with the booking. "
I basically ignored this and continued to ask if tech support could advise what was the issue and all of a sudden I was chatting to a new agent who said they were working on adding the flight and shortly after advised it was done! Their explanation was:
"The error is with re-issuing a points booking with Iberian Airlines. It wont allow a tax quote. Each tax for all the airlines have to be calculated separately which isn't the normal procedure. "
So thanks to a couple of very helpful QF agents (Melody and Kaz) who persisted with a system that didn't want to cooperate I got there.
Also the itinerary was re-ticketed within about 2 hours so didn't have any nightmares with lost bookings that others have experienced.
So if your itinerary complies with the rules be persistent - especially, it seems, if you have Iberia flights in your itinerary
Thanks Danger and others for suggesting pushing back - I was ready to admit defeat.
So, I tried the text late this afternoon. After a bit of to-and-fro, we eventually got on track.
This is an extract:
Q: For any changes made to my existing bookings from 18th September, change fees aside, will the cost of my award be 280,000 points, or will it be re-assessed as 318,000 points, please?
A: I believe that your booking will still be honored.
Q: Thank you. So, do I take it that my Qantas OneWorld Award bookings, made for 280,000 points prior to 18th September, will not be re-assessed as 318,000 points for changes after that date. I understand that normal change fees may apply. The Qantas website seems to lack any information on this.
A: You are correct. You will only be looking at the change fee of 5000 points + any changes tax differences.
However, I'm not really convinced. Is this an opinion rather than fact? I would advise anyone who is after an answer to do webchat or text for themselves.
Edited: For content. "Q:" and "A:" added for clarity
Unfortunately I think they're wrong and changes made after September 18 to bookings - no matter when they were initially made - will be charged at the new, higher points levels.
The reason I say this is that after making my initial OWA booking several weeks ago and having 280,000 points deducted per passenger I've had to make 4 separate change requests. Looking at my points account, on each occasion my account was credited back the 280,000 points and then re-charged 280,000 points plus the 5,000 points change fee (per passenger). In effect the original transaction was reversed and a whole new points transaction was processed - and tickets reissued.
Just my opinion - I too haven't seen anything concrete from Qantas