[DKnoll]

I got the trial. Gave me a 201 area code number. Called it and it waited some seconds after answering, played a DTMF tone and hung up. No, I didn't test it with Duo (lol). Every time this number receives a phone call it increments a login counter on the dashboard.

[floatingatoll]

You may want to contact Twilio abuse and ask them if they operate that number, and if so, point them to the terms of service that issued it and note that they appear to be a flight-by-night credential harvester.