I can get a cell phone within a few blocks of basically anywhere I am.
The carriers make money selling calls and data: not phones.
And while I'm talking about this kind of thing... I can go anywhere and get "free" wifi: even at Circle K. Ya. They have free wi-fi at the Circle K. I can sit at a coffee shop, get a 3 dollar coffee, and work all day. Restaurants are the same.
Admittedly, the internet speeds to the USA are not that great. However, internal to Vietnam, they are really good.