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/, that is 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. | |
| 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 |
Carrier registry links
External Link Notice: The carrier registry URLs listed below are maintained by individual carriers and may change over time. These links were verified as of May 2026 but carrier websites are periodically redesigned.
If a link doesn't work:
- Search for "[Carrier Name] CNAM registry" or "[Carrier Name] caller ID registration"
- Visit the carrier's main website and look for the support/business services section
- Contact the carrier directly for the current CNAM registration process
Carrier registry links:
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?
International Caller ID Registration
US-Centric Feature: The caller ID registration process described in this article is specific to US telephone carriers.
International considerations:
- Canada:
- Some Canadian carriers support CNAM registration
- Process varies by carrier
- Not as standardized as the US system
- Contact your Canadian carrier for availability
- Other Countries:
- Most countries outside North America do not use the CNAM system
- Each country has different caller ID systems
- Caller ID display depends on:
- Local telecom regulations
- Carrier technical capabilities
- Recipient's phone/carrier settings
- Recipient's phone/carrier settings
If calling internationally from Zendesk Talk:
- Your registered CNAM (US) typically won't display outside North America
- Recipients may see:
- Your phone number only
- "Unknown" or "Private number"
- Country code + number
- No caller ID at all
Alternative for international calls:
- Use local phone numbers for countries you call frequently
- Recipients are more likely to recognize a local number
- Some carriers have better caller ID support for local numbers
For more information on Talk errors, see What are the most common Talk error messages?