The Austrian Federal Ministry for transport, innovation and technology (bmvit) provides a new service: The agency for passenger rights (apf) handles requests and complaints regarding transportation by train, bus, ship or plane. It acts as an arbitration body, which means that it is an objective and independent mediator between two conflict parties. It does not take sides and aims at out-of-court solutions.
On the website of apf (available in German) you find information about which cases the agency handles as well as all necessary documents to file a complaint.
In the following video, the agency presents its service (German):