Qantas — can't pre check in

I am flying with my 2 sons to South Africa and wanted to "Check In" online, because you have to stand in unbelievable queues at Sydney Airport. (All International flights stand in the same queue) Clicked on "Online Check-in" entered my "Booking Reference" and "Surname" On next screen selected "Check-In" Get to STep 1 of Online check in and it shows that I have already completed my check in and lo and behold, I'm "Saudi Arabian" as well. Phone Qantas - hold on for 20 minutes and get told my check in doesn't show as completed on their side and I'll have to check in at the airport. Doesn't matter how I explain that I haven't done any check in AT ALL and never mind my concern that someone has checked in ??? - even have my passport no there and everything. All that matters on the 13 13 13 side is that I have not completed my "Check In" and nothing can be changed on their side and I have to check in at the airport. Now I have to write a letter of complaint and post it, because there is no Complaints email address AND I have to go stand in that queue for who knows how long, and hope that there isn't some other person who somehow has stolen my identity and I land up not being able to get on this flight tomorrow.