The most expensive tickets to Bali ever,

I bought tickets online, for me and my daughter to go to Bali for the long weekend on 1/4/12. Unfortunately my daughter couldn't travel that time and I had to call them to change dates and one of the passengers.
I knew I had a non flexible fare, so I was aware I have to pay. Going for economy, I searched on the Internet for dates when tickets price were lowers than what I already had paid.
When I called I asked for changing dates and one of the passengers for my booking, they informed me that changes in the name of a passenger would split the booking. It means now each person would have a different booking reference. Everything else seemed normal, so I paid what I was told to pay ($110). I never received any invoice for this.
The day of my flight the girl at the counter couldn't find my reserve because according to their system I was supposed to fly days ago (on the date of my original booking). What happened was the girl never changed my booking. She just changed the second passenger but not mine.
To resume, I had to pay for my tickets again that day at the airport. It costed twice that the first one. But as I was sure of their mistake them, I set a complain sure that they would understand my reasons: I never call them to ask split the bookings in order to travel different days, and someone from their team made a mistake. All that was clear like water and they will give me my money back. That is what I thought.
But it seems like I was very naive to believe that.
Jetstar responded avoiding all responsibility. According to Michael Marabito (who sigh the letter), it was my fault as I choose a inexpensive fare. he also recommended me if I have a travel insurance, to try to recuperate the money I have lost, threw them.
Obviously I am not happy with Jetstar response to avoid any responsibility and to dare blaming ME for choosing a cheap fare without understanding its limitations.
I just wonder if there is in Australia other instance where to raise complains again those big companies. Are we on their mercy? I know I am not going to fly again with them. But then with who? Qantas with his uncounted labour injustices? Virgin is not much better as far as I know.
Once before I had a similar situation, but this time I was with Air NZ. Their solution was pretty different. unfortunately they don't fly domestic. :(