Australia, being a federation of states and territories, has both federal and state consumer protection legislation. Each jurisdiction provides recourse to a tribunal.
Tiger Airways is a listed corporation and is therefore subject to federal legislation, in this case the
TRADE PRACTICES ACT 1974
The Australian Competition and Consumer Commission (ACCC) investigates consumer complaints against corporations, including allegations of misleading and deceptive conduct. I suggest your relatives look at the ACCC's web site -
Misleading & deceptive conduct - then click on the link to the 'how to complain' procedure and follow the steps set out therein.