Belong have come out with new mobile plans. Includes data banking, no contract and ability to customize call allowances.
5GB starts at $25/month
15GB starts at $40/month
First month get double data (which can be banked I believe, not 100% sure)
Add your call allowances (if needed)
$5/month for national calls+text
$10/month for national and international calls+text
Coverage details here https://www.belong.com.au/mobile/coverage-map
Do these guys have access to the full Telstra network?