Toll-Free US numbers are designated for business messaging use by all major carriers in the United States, and by most major mobile carriers in Canada. This makes Toll-Free numbers a popular alternative to long code or short code numbers in the US and Canada. 

Toll-Free Verification is currently required in the US and Canada for best delivery. Please complete the Verification process as soon as possible to avoid traffic being blocked (Canada) or traffic subject to increased filtering and daily limits on sending (US). For more information see What happens if I don't complete Verification. This is part of the process to verify all Toll-Free numbers and align sender visibility with the Short Code and 10DLC messaging channels. If you’ve already verified your Toll-Free numbers, no further action is needed.

Effective October 1, 2022, Twilio will apply a daily limit of 2,000 messages a day for messaging sent over unverified Toll-Free numbers in the US. For more information about these daily thresholds, see What are the new Industry-wide thresholds for sending traffic over Toll-Free numbers.

Important Note: Unverified traffic that exceeds the daily limit or is filtered for spam will see a 30032 error code returned for both scenarios. To avoid this, we recommend submitting your number(s) for verification as soon as possible. Submitting your completed verification form to the carrier places the Toll-Free number(s) in a Pending Verification status, which allows for a higher daily volume and greatly reduces the chances of filtering while waiting for final carrier approval. The unverified Toll-Free daily cap is a daily maximum limit, (not a guaranteed daily minimum), so unverified traffic can still experience message filtering even when well below the daily limits.

see more...

Also, see Messages from unregistered numbers may be filtered or blocked.