GIVE ANSWERS - English

hi, here i am.
i really thanks u.
i wuold have a question.
a few days ago i was watching a tv programme and one of the guys who talking say this:
"So they don't have refrigereted trucks or......."
why did he use "don't + have" instead of "have not"? is there any kind of reason? or both them can be used indifferently?

hi, thank you.
i have not the possibility to get on the internet often, so i'm sorry if answer late.