Don't hesitate to contact the QBCC if you have a complaint to make against recalcitrant builders who won't or can't pay and are withholding your retentions.
Here is a link to the home page https://www.qbcc.qld.gov.au/
The phone number is:
An alternative number and fax is:
Phone +61 7 3613 3063 Fax +61 7 3225 2929
the contact email that I use is QBCC Complaints