How to decide the boundary line between being polite and being firm? [closed]

I was returning home via a domestic flight this week. Now, I am a vegetarian and absolutely can't consume non-vegetarian food (it's a matter of belief).

During the flight, I received non-vegetarian meal despite having told the flight hostess that i wanted a vegetarian one. I realise it might not seem like a big deal, but I felt the need to file a small complaint in the office concerned. At the same time my gut feeling told me i was simply over-reacting to a small incident and should just consider it as their small mistake. I did end up filing a complaint after the flight.

I'm not sure if I made the right decision now. Was I wrong in what I did? I do realise they have a lot of work on their hands and this might come across as being rude, but at the same time i think that they need to act more responsibly.