Issue

When I place an outbound voice call, I get the Talk error: Cannot connect to number.

Resolution

Ensure the number uses the international format E.164. For more information, see What are the accepted phone number formats for Talk?

If the number is formatted correctly and the error persists, the callee or their external carrier might’ve blocked the number. If the individual callee blocked the number, try to call from another Talk number to find out why the end user blocked it.

External carriers use phone number reputation systems. If a number's reputation score reaches a threshold, the carrier can block it.

To resolve this, report the Talk number you use to call to the destination carrier. You can register your number at https://www.freecallerregistry.com/fcr/, a shared database that multiple providers use to share caller reputation.

See the table below for common carrier registries for number reputation.

Carrier Notes Registry
Verizon Verizon provides a link to help mark a number as allowed. However, Verizon still passes the information to its third-party vendor.

https://voicespamfeedback.com/vsf/

https://reportarobocall.com/trf/#
Sprint https://reportarobocall.com/trf/#
US Cellular https://reportarobocall.com/trf/#
Hiya Hiya services some major carriers and numbers outside the United States. https://hiya.com/manageyourcallerid
AT&T Wireless AT&T uses the vendor Hiya. AT&T Mobility Services indicates to report the number through Customer Care Support, or by registering the number with Hiya. https://hiya.com/manageyourcallerid
Note: Phone number reputation can take time to update. There’s no guarantee on how long it’ll take for the block to be removed. Continue to monitor the situation and report the issue to the external carrier.

Register your business and Talk numbers for Secure Telephone Identity Revisited and Signature-based Handling of Asserted information using toKENS (STIR/SHAKEN) and Calling Name (CNAM) to improve call acceptance rates. After you register for CNAM, carriers associate the number with a valid company and improve the number's reputation. To get started and see the full list of requirements to register for CNAM, see Does Zendesk support CNAM?

For more information on Talk errors, see What are the most common Talk error messages?

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