What is the proper name for numbers you can text to get info/promos?

Usually they are 5 or 6 digits that a company or organization sets up.

They put up some kind of billboard or sign that says for example “Text ‘a phrase’ to 5545”

When you text “a phrase” or whatever key word they give you, you automatically receive a text message back that says something along the lines of “Thanks for texting ‘blank’! If you would like to continue to receive updates from us text “Y”. If you would like these updates to stop, reply with “Stop”.

These were also used when the earthquake hit hati.

So what is the Proper Name for these Incomplete Phone Numbers???