They're not toll numbers. They're regular numbers. Mobile networks get paid a small amount of money for delivering SMS messages. Let's say that they get paid $0.003/message. Let's say you're a small mobile network and I bribe you or make a deal with you: I'll get lots of messages sent to mobile devices on your network and you'll pay me $0.001/message. That's good for you as the mobile network and good for me since I get money.
So I get a list of numbers on your network and start filling them into any form that will send a text to that number.
There is no "don't send messages to scammer toll numbers" option because these aren't toll numbers. They're regular numbers. I mean, Twilio could probably easily detect this behavior themselves and prevent it. As they note, they often cycle through adjacent numbers and do it in a quick fashion. However, the numbers aren't scam/toll numbers as a category. You'd need to use ML/heuristics to find these.
Yeah, but they could do it as part of their basic service because it would make customers happy. They don't though, because they also make money from it
When the service provider is liable for fraud losses they use the latest best practices. When the customer eats the loss they can just throw up their hands and say you should have used xyz security feature.
