When an SMS complaint to the master and a written complaint to the company under MLC 2006 Standard A5.1.5 have not produced a remedy, you have the right to escalate directly to the flag state. Every flag state operating under MLC 2006 is required to maintain a complaint procedure for seafarers and to investigate seriously. The flag state can compel the shipowner to act, suspend or withdraw the Maritime Labour Certificate, and detain the vessel. Filing a flag-state complaint does not waive your other rights — you can still contact the ITF, the port-state administration, and the next port-of-call's PSC office.
MLC 2006 Standard A5.1.5 (on-board complaint procedures) and Standard A5.2.2 (flag-state inspection and complaint handling). Flag-state administration contact details are listed on the IMO GISIS website. The flag state must investigate complaints and report back; major flag states publish annual MLC complaint summaries.