Issue

If you receive an "invalid number" message when calling using a Bulgarian toll-free number provisioned through Twilio, this article will help you understand the likely causes and guide you through troubleshooting steps.

Key Points

• Bulgarian toll-free numbers on Twilio are designed for inbound voice calls only.
• Outbound calling from these numbers is not supported.
• Inbound reachability may be restricted to calls originating within Bulgaria.
• Issues may also arise due to dialing format, carrier restrictions, or pending regulatory requirements.

Cause

1. Outbound Calling Attempted:
   Bulgarian toll-free numbers cannot be used to place outbound calls. Attempting to do so will result in errors such as "invalid number."
2. Dialing Format Issues:
   Ensure the number is dialed in the correct E.164 format. Incorrect formatting can cause calls to fail.
3. Geographic Restrictions:
   These numbers are typically only reachable from within Bulgaria. Calls from outside the country may not be completed.
4. Carrier or Regulatory Restrictions:
   Some carriers may block calls to toll-free numbers, or there may be pending certification or compliance requirements.
5. Configuration Problems:
   Misconfiguration in the Twilio Console or your application can prevent calls from being received.

Resolution

1. Verify Number Capabilities:
   • Check the Twilio Console or Twilio Voice Pricing - Bulgaria to confirm the number’s capabilities.
2. Check Dialing Format:
   • Ensure callers are using the correct E.164 format (e.g., +359800XXXXXX).
3. Test Inbound Calls from Within Bulgaria:
   • Attempt to call the toll-free number from a Bulgarian carrier. If the call does not connect, proceed to the next steps.
4. Collect Call Examples:
   • Gather recent examples (within the last 24–48 hours) of failed inbound calls, including:
     • The calling number (From)
     • The toll-free number dialed (To)
     • The exact date and time (including timezone) of each attempt
5. Check for Regulatory Notifications:
   • Review your email and Twilio Console for any requests for additional documentation or compliance steps.
6. Review Number Configuration:
   • Ensure the number is configured for inbound voice in the Twilio Console and that your call handling (TwiML, webhooks, etc.) is set up correctly.

Next Steps

If you have confirmed the above and are still experiencing issues with inbound calls (calls not appearing in your Twilio call logs), collect the call examples as described and reach out to Twilio Support for further investigation. Providing detailed call examples will help expedite the troubleshooting process.

Additional Information 

Below you will find references to useful documents:

• Twilio Voice Pricing - Bulgaria
• E.164 Number Formatting Guide
• Configuring Phone Numbers in Twilio Console
• Bulgaria Guideline
• Toll Free Phone Number Restrictions and Limitations

Note: Outbound calling from Bulgarian toll-free numbers is not supported by design. For outbound calling needs, consider using a different type of Twilio number.