Hmmm. . . the Spanish movie with the subtitle that used "aqui" instead of "aca" which was actually said is from Argentina. I'm going to guess that the subtitler was from a country that doesn't normally use "aca" but understood what it meant so he/she decided to correct the bad Spanish spoken by the Argentinian (LOL).
Just a note on "che":
It means something like "Hey! or "Hi!" in Argentina, but it can mean "Oh dear!" or "Who cares!" or "So what?" in other parts of the Spanish-speaking world.
#10,
You might be right, or it might just be a case of practicality - they wanted a more univerally accepted style. I teach AP Spanish. At an AP conference, one of the presenters was an Argentinian. I asked him if, when doing free response orals or writing essays, if he believed the use of the vos forms was okay. He said that although it is officially accepted in Argentina, and although he uses it, he advices his students not to use it because of possible confusion and/or bias from the graders.
Knowing your audience is important - especially if you want to sell something.
Actually both "aquí" and "acá" are correct. The first is just more common in Spain and the second in hispanic America.Since many text books are published in Spain you may find "aquí" written there more often than "acá"
As for the "che", my guess is it comes from Valencia, where it is very popular and used the same way as in Argentina. How it managed to cross the Atlantic from Valencia to Argentina, I have no idea, since most of Spain´s immigrants to Argentina come from the North/Nortwest or the Canaries.
Perhaps there is something similar in Italian that was brought by the huge pool of immigrants from Italy and "españolizado" once in Argentina.
That could explain it, because there used to be a big connection between valencia and italy´s western coast not so long ago.

