Jetstar engaging in extortion

While making a reservation online, I selected my payment method and agreed to the terms. After I was charged, the screen displayed an error message indicating that the fare I was paying for was no longer available and I would have to pay more - AFTER I WAS CHARGED THE ORIGINAL FARE. There was no email from Jetstar with the reservation details. No indication at all that the reservation was even made! Just an email (from PayPal) that I had been charged the original fare!

I was able to determine that a reservation did in fact exist after ringing and waiting on hold for 20 minutes. The Manila parrot I spoke to and her so called supervisor refused to even listen to me and insisted that I had to pay the extra.

Now I'm no lawyer, but if I'm quoted a price which I agree to pay, what do you call being asked to pay more after actually paying the agreed price? EXTORTION!

Australia-Melbourne - Tullamarine