People or Persons or Person?

I am REALLY sick with this.

You all help me with this, okay?

Here goes!

Let's say, the scenario is, you are queuing to buy tickets to watch some movie.
And so, is finally your turn~ so mostly you will say ~~~ ( I use Avatar for example )

" Avatar, 4pm for two "
or
" Avatar, 4pm for two people "
or
" Avatar, 4pm for two persons "

Am I correct so far?

For me, I use "people" ~ instead of persons.
If just one, you will say " one person"
If more than one, is " people "

I am correct, right?

BUT! WHY everytime I said " 2 people " they will look at me and said " 2 person? "
Not "persons"! but "person"!!!!!
;(

Please tell me, whose right and wrong?
Or ... is this part of Malaysia's habit ?????
Please enlighten me

-Dino-chan-