Lies, lies and more lies!!

I booked a business class return flight from Sydney to Honolulu. At the last minute our flight from Honolulu to Sydney was cancelled. We were advised by email (no phone call so only pure luck I checked my emails!) the reason for the cancellation 'operational issues'
I called the call centre immediately and was told we would be transferred to a Qantas flight on the following day which would be business class as we wouldn't be downgraded and the flight was leaving at 1.45pm. I was also told a new itinerary would be emailed within 24hrs. I was offered no help with accommodation and given it was the busiest public holiday weekend (4th July) we were lucky to find accomodation somewhere!
The next day I still had no email and as I was missing another flight and booked accommodation due to this I called again to follow up. Again I was told the same flight details and again confirmed as business class.
Later that day as I still had no email I called Qantas to confirm we were booked on the flight. They had no record of us.
I checked online for the flight we were advised and no such flight existed. The only Qantas flight leaving that day was at 10.15am! so I called Jetstar again to see what was going on. They were little help and advised us it might be better if we just went to the airport early.
So we went to the airport early and straight to the Qantas service desk. They handed me economy tickets!! I informed them this was incorrect as we were advised by Jetstar they had transferred us to business class as per the tickets we paid for. We were told the flight had no available business class seats as they were full and there was nothing they could do. I asked to speak to someone in charge as we were not accepting this.
The manager came over, and she called Jetstar directly to confirm. She then advised us that Jetstars response was that we could fly economy and they would refund our fare as we were unable to be flown business class.
We were less than happy but if we didn't take this option we wouldn't have been able to fly home that day.
Once home I called the call centre to follow up my refund as per what I had been advised at the Honolulu airport. I was told to lodge an online complaint - which I did
It took them nearly two weeks to call me - I was informed today I would not be receiving a refund. Their excuse is that Qantas is a full fare airline so the cost of the Qantas economy ticket and Jetstar business ticket is similar. They also said that given we boarded the economy flight that means we accepted this.
I completely lost it!! I gave her the complete run down of what had occurred and what we had been promised. She asked "do u have anything in writing confirming you would be given a refund?"
"No I responded, because you wouldn't give me ANYTHING in writing though this whole process!"
She says "a new itinerary was emailed to you on 4/7"
I told her I never got the new itinerary which is why I called multiple times asking for one. So I asked her what the itinerary confirmed. She told me it confirmed the Qantas flight details. I asked "what class", she said "business class"
So I asked her to email it to me there and then. She told me she would be unable to do that. I asked is that because it would give me further evidence against you?... I again asked her to send it to me and she said she wouldn't be able to.
I don't think I have ever been as angry in my life! How on earth do they think they can get off with this? They tell you whatever they can over the phone to placate you, won't back it up in writing and then completely do the opposite of what they promise you! This really isn't good enough and they can't get away with it!
Has anyone else experienced this? What did you do about it?.....I am going to contact consumer affairs and the airline advocate now to see where I stand.