[plasma]

I've only briefly played with Twilio, but would it be possible for your app/TwilML to intercept the request to send a text to those numbers, and detect a volume of X messages being sent to the same number (highly unlikely) and abort?

[ksajadi]

That's one of their recommendations. So the idea of Twilio is just drop a library and we take care of telephony for you, but then they suggest you implement cooldown periods, exponential backoffs, use their other services (paid) to check if the number is a mobile etc. And they tell you this, after you get the nasty bill.