Working And Didnt Get Paid(netherlands)

Hello, a friend of me came to the Netherlands 2 months ago and started working in a Greek restaurant, the owner is like the majority of Greek business owners, he is using and ripping off people in order to make more profit. He knows that the Greeks that comes here doesnt know anything and what in Greece is normal to work without contract, a Dutch person cant imagine how many 'cash in hand' jobs you can get in Greece. So the owner was using different excuses to buy time and after 26 days my friend didnt have a contract, didnt get paid and when he said that he must leave the job because he doesnt have money, the owner said that he will not get paid if he leave suddenly, i am suspecting what he is using people in general because he doesnt wanna pay them and he makes the place a hell so they are leaving themselves and because is time consuming + needs to have some knowledge on how to do it, most of the people are not going legally against him. Unfortunately i didnt know that he was here because we had a conflict but he messaged me yesterday and he told me his story, i would like to help him to get back this money and screw this pig restaurant owner. After 26 days he didnt have contract, didnt get any money and they didnt even help him to make a BSN, we have only some messages on Viber with the owner of the place. There is something i can do ??? Thank you in advance