Issue
Twilio customers sometimes experience call rejections from downstream providers when placing calls using a verified caller ID (a number not owned by Twilio), even after registering numbers with Twilio Voice Integrity. This article explains why this happens and how to maximize call deliverability.
Symptoms
- Outbound calls using a verified number (not a Twilio-owned number) are rejected by the provider.
- Calls placed with Twilio-owned numbers are more likely to be delivered successfully.
- Example error: “Provider declined call” (Call SID may be provided for troubleshooting).
Product
Programmable Voice
Environment
Twilio Console
Cause
Voice Integrity is a Twilio feature designed to improve call reputation and deliverability by providing attestation and trust signals to downstream carriers.
- Voice Integrity protections and attestation features only apply to Twilio-owned phone numbers.
- When using a verified caller ID (a number you’ve verified but do not lease from Twilio), Voice Integrity cannot provide the same level of attestation or reputation management.
- Downstream providers may require certain trust signals to accept calls. Without these, calls are more likely to be rejected or blocked.
Resolution
-
For best results, use Twilio-owned numbers registered and enabled for Voice Integrity.
These numbers benefit from full attestation and trust signals, improving deliverability and reducing the risk of rejection. - If you must use a verified number, be aware that it may not receive the same protections, and provider rejection is more likely.
- Review your use case and consider switching to Twilio-owned numbers for critical communications.
Additional Information
- If your project is business-critical or you require faster response times, consider upgrading your Twilio support plan. Higher-tier plans offer priority handling and expedited support for urgent issues.
Below you will find references to useful documents: