[tomasreimers]

You can check if a number is using Twilio via a special number: https://www.twilio.com/en-us/blog/lookup-phone-carrier-recor....

[blackeyeblitzar]

Or a site like https://www.freecarrierlookup.com/ which works for every number

[yakovsi]

Twilio has a concept of "hosting a number", meaning, the original carrier retains the number, only SMS is handled by Twilio. So parent's link will be more accurate for this application.