I'm curious about what short codes can carry extra charges like this. For regular phones, people are generally aware that 900 numbers are toll lines and you'll

I'm curious about what short codes can carry extra charges like this. For regular phones, people are generally aware that 900 numbers are toll lines and you'll be charged for that, but for these text numbers I don't know what the rule is. Seems like there's a lot of potential for scammers to tell people to text a certain number without telling people that charges would apply. At the student newspaper I used to work for, we told people to text "follow name" to 40404 (Twitter's short code) to get text message updates with news.