Jetstar continuing "Sales" despite not honouring bookings!!

I bought direct flights from Adelaide to Hobart in September as part of a highly advertised sale. Three weeks later, I logged into my Jetstar account to find that the flights had been changed. Jetstar did not contact me to advise there had been a change. Both flights were changed from direct flights to two seperate flights each way with a stop over in Melb. The return flight went from a 1.5hr duration to over 8hrs (with a six hour gap between arriving and departing Melb). I contacted Jetstar and was told that the flights had been changed due to staffing issues yet the same day they continued to advertise more 'Sales' on TV and the internet.
How can a business continue to sell a product that they can't honour? How can a company take money from customers for a product only to cancel the product without notifying the customer? I believe the company is deliberately over-selling flights to make money, then booting people off flights and refunding their money so Jetstar can bank the interest. Jetstar's business practices need to be investigated by the ACC because they continue to advertise cheap flights that they are cancelling regularly after taking customers money.