Grill'd are scumbags. As mentioned in the linked article, they exploited supposed traineeships to underpay staff (among other labour violations). From what I can tell, they continued to do that for about a decade after it was called out.
Article from The Age in 2015: https://www.theage.com.au/national/victoria/grilld-contracts-under-scrutiny-as-sacked-exworker-takes-burger-chain-to-court-20150722-gii2hl.html
Union article indicating a resolution after industrial action in 2025: https://www.weareunion.org.au/after_paying_its_staff_less_than_minimum_rate_for_years_grill_d_buckles_under_union_pressure