21268: Sending to Premium rate or Information Service numbers is not allowed

You can't send SMS messages to premium rate or information service numbers through Twilio. Twilio classifies premium numbers as higher-cost numbers for special services, and Lookup Line Type Intelligence identifies these destinations with the premium line type.

• The To number is a premium rate or information service number, which Twilio does not allow as an SMS destination.
• Your application submitted a destination number without validating its line type first. Lookup Line Type Intelligence can identify whether a number is premium before you send the message.
• Your application accepts user-entered or international destination numbers, which can expose your account to premium-rate fraud attempts in high-risk geographies. (help.twilio.com)

• Send the message to a standard SMS-capable recipient number instead of a premium rate or information service number.
• Validate destination numbers before sending. Use GET /v2/PhoneNumbers/{PhoneNumber} with Fields=line_type_intelligence and reject numbers whose line_type_intelligence.type is premium.
• If your application allows broad international sending, review your SMS Geographic Permissions and block countries you do not intend to message. Twilio recommends limiting destinations to reduce exposure to premium-rate fraud. (help.twilio.com)

• Line Type Intelligence
• Messages resource
• International SMS Messaging Geographic Permissions and How They Work