Effective September 10, for new phone numbers provisioned through the existing Phone Number Provisioning API, address requirements will be enforced via the API, provided through an AddressSid. This means you will be required to provide addresses for newly provisioned regulated phone numbers. API calls to provisioned phone numbers that do not submit a valid address will fail with error code 21631. Only API calls provisioning numbers outside the US and Canada that fail to send an address are affected.
Additions and changes to the Twilio platform