HOW IS JET-SCAR STILL IN BUSINESS???? PLEASE STOP USING THEM SO THEY GO BUST

I was booked on a trip to Oz for the first time to visit my Mum and we were due to spend Xmas in Perth and then fly to Cairns for New Year. Unfortunately due to me starting a new job I had to cancel my plans and miss my trip. Luckily my flights from England to Australia were booked through Emirates - who are a reliable reputable company and they have given me full refunds for these. Unfortunately the internal flights were booked through Jetstar (or Jetscar as I have now dubbed them - due to the permanent scarring left on my brain through sheer exhaustion of dealing with such an incompetent bunch of fools!)
Before any Jestar lovers leap in to defend your beloved airline - I have flown with many airlines and we have our fair share of crap budget airlines in the UK (Ryanair, Easyjet, Flybe) but you get LOW fares not the over inflated ones chargets by Jetscar. So you accept that you sacrifice any form of customer service by making the saving on your wallet.
Whilst I agree that you should have to pay fees to make any changes - this is standard with all airlines and normal practice - what I discovered about Jetscar shocked me. They actually get away with INCREASING the price of a flight you have already paid for!!!!
How can a company legally charge you more for a seat that is already paid for and yours???? It would be like me buying a TV from Argos for £150 in the sale.....then them knocking on my door 2 weeks later to say "you owe us £200 sir because the TV you purchased has now gone back to £350. Plus you now have to pay for our taxi to your house and back to our office which will add an extra £59 onto the total cost.
For an Airline to be this bad that it has its own special complaints website - why do you guys in Oz still use them? Book elsewhere & let them go bust!
Companies that outsource their call centres abroad to make additional profits for the Executives by paying low wages to poorer countries should flag up as dodgy for starters. Would expect to get any kind of assistance? Every "operative" I've spoken to on the chat function is clueless and barely understands English. They ignore questions asked to them and instead are only concerned with selling you additonal services and quoting ever changing figures.
My query was simple - I needed to pay an additional fee to allow changes onto my booking. The confusing part was that I had to pay a fee to have a no fee service, that would prevent me paying any fees.....but they were adding additional fees onto this to do so and then more additional fees when I wanted to make the changes.....oh & of course the customary Jetscar fare increase.
So for a flight that cost $400 they wanted an extra $600 to change it to a flight that would only cost $450 at its time of booking next year!!!!
Again I stress why anyone actually gives this company your hard earned money!

When I make my trip to Oz next year - I shall be avoiding this company....

Domestic
Australia-Perth
Australia-Cairns