I've heard people say Anna with the A sounding like how'd you say Annie. But in the movie it's pronounced differently. How do you like to say it? :)

I've heard it pronounced both ways. But I assume that On-a is the correct way, since it's way it's done in the movie.

that's how it's supposed to be pronounced.

I would assume the only people who don't haven't seen the movie yet (only read the names online or something) or just dislike pronouncing foreign names properly.

like they say it in the movie

I say Ah-na.

I say "Anna" the way it's typically pronounced here in the US: An-na.

It's not because I dislike pronouncing foreign names correctly (I'm usually a stickler about accuracy, actually). What happened with Frozen is that I first saw it ~8 months after it came out. By then, I'd seen loads of articles and whatnot with the characters' names, and my assumed pronunciation of Anna stuck.

Then again, I'm also one of the weird people who says "air-ee-ELL" instead of "aerial". So maybe I'm not that much of a stickler after all.

Ah-na.
If I were to say On-a in my accent it would sound hella strange.

I think I pronounce it like "A sounding like an O", but I personally pronounce A as A how I'm always used to, but that's just because English isn't my first language. A in Annie sounds more like Ä to me and I think Änna sounds really weird. In English version of the movie they say Anna pretty correctly most of the time but sometimes they say too short "n", they say Ana instead of Anna.

^Like Zeppie.

That is how we pronounce it in Norway.