Upvote:10
Well the first question would be, how did your son get to Australia? Did United, STA and/or ANZ sort out a flight for him and you are simply wondering who to seek some compensation from for the hassle? Or did you have to buy a new last minute ticket?
If you had to buy a new ticket, then STA is the one you need to work with to get the previous ticket refunded. They are the agency of record and all payments go both ways through them (especially since it may well have been a consolidator ticket, as STA is a huge ticketing group). Ultimately they have to get the funds back from whichever airline is the marketing carrier and may delay the refund using that excuse, but STA should be big enough and professional enough to pony up the refund before they finalize with ANZ.
If his flights were sorted out without any additional ticket purchase and all you want is some compensation for the hassle or delay if any, I don't want to be pessimistic but good luck. A glitch in the system, a lost data packet or two between computers happens and it is hard to prove blame for anyone party. Your best bet in this scenario is to write the airlines involved a polite, factual letter outlining the issues and hope you reach a caring ear. You may get something like extra frequent flyer miles, maybe get real lucky with a voucher towards a future trip, but don't count on any major compensation.