Twilio's own lookup API will tell you if they are the carrier with I assume pretty good accuracy. It works on the number I own with Twilio.

Some of the political texts I get show twilio as carrier. Calls tend to be Onvoy which is now Inteliquent I believe.

Will also show who the carrier is believed to be if not them.

https://www.twilio.com/docs/lookup/tutorials/carrier-and-cal...