I have 2pax ticketed and paid for Ex-CAI fares departing in Sep with Qantas. CAI-xMAD-xDOH-DPS-xKUL-NRT,HND-CTS-xHKG-PER-SYD-DFW-SEA-DFW-SCL,GRU-DOH (16 sectors with the TYO change and open jaw).
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You also have to count NRT-HND and SCL-GRU.
A map from the Great Circle Mapper - Great Circle Mapper
Are you wanting to just change dates or routes? Changing transits<---> stopover can be more involved if real govt taxes change.
Do you have an issued 081-xxxx e-ticket from Qantas for a 16 segment *ONE*?
You are playing with fire trying to get QF to change, unless you are QF Plat OWE so get the better Hobart call centre. Are numerous posts on FT and AFF of (in experienced) QF phone agents making errors when rebooking more complex fares. Some of these errors have been terminal.