Use "it" to refer to company itself, as a unit use "they" to refer to people who work at the firm- It´s the same case when you talk about a country: "it" refers to the nation as a unit; "they" refers to the people who live in that country-

It depends. There are many reasons to use either. One reason to use "they" is that the company is a collection of people working so it might sound better to make the company seem like one giant person doing or saying something. One reason to use "it" is that the company is also a system and has a function so it might sound better to to make the the company seem like a big business. So you must decide if you want to represent the company like a person or a thing? Another thing to consider is that "it" feels a little less human than "they" and is slightly more negative sometimes. It's complicated, but if you listen to a lot of talk about businesses then you will get used to it.

They are making a movie about the return of the seagulls. It is making a movie about the return of the seagulls. Which one sounds better? I like THEY