Fishmonger sold me spoiled products

Bought couple of fish fillets (for a cheap price tbh) from a fishmonger in Dublin. I froze one, but used the other two. After frying the first one, I threw it away as it was smelling disgusting, but made the mistake to make a soup out of the second and eat it (as it was not extremely slimy or smelled that bad). After taking the third one out of the freezer, I saw that maggots were trying to escape from inside the fillet. I was obviously disgusted, but I am unsure of how to handle this situation, and I would appreciate any suggestion. Should I let it go, talk to the fishmonger or contact any potential public service? (I also have to add that due to financial constraints, I am kinda dependent on that shop for cheap protein)