# E21031 — VoiceCallerIDAlreadyExists

This phone number is already registered as a caller ID for the workspace.

- **HTTP status**: `409`
- **Type**: `conflict_error`
- **Name**: `VoiceCallerIDAlreadyExists`

## What to do

A phone number can be registered once per workspace. List the workspace's verified numbers to find the existing registration's ID, then delete it before registering the number again.

Operations that resolve this:

- [List verified numbers](/docs/api/reference/list-voice-verified-numbers)
- [Delete a verified number](/docs/api/reference/delete-voice-verified-number)

## Related

- [Idempotency](/docs/api/idempotency): safe retries and key reuse rules
- [E21xxx — Voice & SIP trunking](/docs/api/errors/E21xxx): every code in this range
- [Errors](/docs/api/errors): the full wire contract, status mapping, and error catalog
- [Error handling](/docs/guides/errors): branching on `type` and `code`, validation details, and `vendor_code`

## Related resources

- [Should I use a Bird SDK or call the API directly?](/explained/platform/should-i-use-an-sdk-or-call-the-api-directly) (answer)
- [Build your first integration](/learn/paths/integration) (course)
- [Send your first email](/docs/get-started/send-your-first-email) (docs)

[Get an implementation brief](/learn/workspace?topic=api-basics)