Home Troubleshooting & Error Resolution Resolving T-Mobile Call Blocking with Error 32017 for Twilio Numbers

Resolving T-Mobile Call Blocking with Error 32017 for Twilio Numbers

Last updated on Jul 30, 2025

Overview

If your outbound calls to T-Mobile numbers are being blocked with Error 32017, it's typically due to the number not being properly registered for A2P (Application-to-Person) messaging or flagged as spam. This guide outlines the steps needed to resolve the issue and ensure your Twilio numbers are compliant and trusted.

Understanding Error 32017

  • Error 32017 from T-Mobile indicates that a call or message is being blocked by the carrier due to:

    • Unregistered A2P number

    • Potential spam/scam detection

    • Caller ID (CNAM) not recognized

    • Missing SHAKEN/STIR authentication

Resolution Steps

1. Register the Number as A2P with Twilio

  • Go to Twilio Console → Trust Hub

  • Register your business and link your phone numbers to the A2P 10DLC campaign.

  • Ensure the campaign is approved and active.

  • Use a registered number for calls and messaging.

2. Add CNAM (Caller Name)

  • Assign a valid CNAM (Caller ID name) to your number in Twilio.

  • Navigate to Phone Numbers > Manage > Active Numbers, select your number, and set CNAM.

3. Enable SHAKEN/STIR

  • SHAKEN/STIR signing authenticates your calls to reduce blocking.

  • Twilio does this automatically for registered numbers, but you may verify status via the Trust Hub or support.

4. Monitor Number Reputation

  • If a number has been flagged or reported, consider:

    • Rotating to a new number

    • Registering a new number under A2P 10DLC

  • Use services like FreeCallerRegistry.com to check your number’s reputation.

5. Contact Twilio Support

  • If the number is registered but still blocked:

    • Open a support ticket in Twilio

    • Provide sample call logs, error codes, and destination numbers

Additional Best Practices

  • Use branded caller ID for better pickup rates.

  • Avoid high call volumes or short call durations, which may appear spammy.

  • Educate end users to save your number if it's used regularly.

Need Further Help?

If you're unsure whether your number is compliant or registered correctly:

  • Contact Evo Tech Support with:

    • Affected number(s)

    • Destination number(s)

    • Call timestamps

    • Twilio project SID (if available)

We can help escalate the case with Twilio if needed.