https://www.centrecom.com.au/ claim free postage, but not for me based on my post code, according to Aus Post's calculator it's the same cost as sending from Centrecom's suburb (VIC, 3020) to same suburb in (Victoria VIC, 3020) as it is to send from (VIC, 3020) to my Suburb (4872) in Qld.
https://auspost.com.au/parcels-mail/calculate-postage-delive…
Found this in the T's & C's
"…excludes areas whereby the cost becomes high due to the delivery location’s remoteness, e.g. Kangaroo Island and other extreme remote locations. If unsure please check with us first."