35134: `Messages` array contains duplicate `To` numbers.

This error occurs when your request includes the same destination more than once in the Messages array. Bulk messaging requests use a recipient list, and each recipient entry must be unique.

• The same phone number or channel address appears more than once in the request payload.
• Recipient values were not normalized to a consistent format before you built the request, which can cause the same destination to be submitted more than once.

• Remove duplicate destinations before you send the request. Ensure each recipient appears only once in the Messages array.
• Normalize phone numbers to E.164 or use a consistent channel address format before you compare and deduplicate recipients.
• Validate and format phone numbers before sending so you can deduplicate against a single canonical value. Use Lookup if you need to confirm the format of each number.

• Getting started with the Twilio Communications API
• Formatting and Validation
• Formatting International Phone Numbers