> ## Documentation Index
> Fetch the complete documentation index at: https://docs.open.cx/llms.txt
> Use this file to discover all available pages before exploring further.

# Attach or detach the outbound caller number of a phone agent

> Set an agent’s verified outbound caller number or clear it. Clears the agent’s pool selection and keeps its assigned SIP trunk.

Requires the `phone:write` scope. The number must be verified for the same workspace as the agent. Use `caller_number: null` to clear it.

This action clears the agent’s number pool selection and keeps its assigned SIP trunk. To choose a BYOC pool or a different SIP trunk, open the agent’s **Telephony & Routing → Outbound Caller** setting. See [agent configuration](/phone/agent-config).


## OpenAPI

````yaml put /phone/{phone_agent_id}/caller-number
openapi: 3.1.0
info:
  title: OpenCX API
  description: >

    OpenCX is an AI-powered, all-in-one platform for customer support and
    outbound communications.


    Use this API to manage your OpenCX organization's AI agents, actions,
    conversations, contacts, and more.


    To get started, generate a new API key from the dashboard.


    ## Authentication

    All API endpoints require authentication using a Bearer token. You can
    generate an API key from your OpenCX dashboard.


    ## Rate Limiting

    API requests are rate limited to ensure fair usage. The current limits are:

    - 100 requests per minute for standard endpoints

    - 1000 requests per minute for streaming endpoints


    ## Error Handling

    The API uses standard HTTP status codes and returns detailed error messages
    in the response body.
  version: 1.0-beta
  license:
    name: MIT
    url: https://opensource.org/licenses/MIT
servers:
  - url: http://localhost:8080
    description: Development
  - url: https://api.open.cx
    description: Production
security:
  - bearerAuth: []
paths:
  /phone/{phone_agent_id}/caller-number:
    put:
      summary: Attach or detach the outbound caller number of a phone agent
      description: >-
        Set which of your verified phone numbers this agent presents as caller
        ID on outbound calls (including campaign voice steps) — or pass null to
        detach. The number must already be verified for your organization;
        purchasing and verifying numbers is done in the dashboard. The agent's
        SIP trunk assignment is not affected.
      operationId: setPhoneAgentCallerNumber
      parameters:
        - schema:
            type: string
          in: path
          name: phone_agent_id
          required: true
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/SetPhoneAgentCallerNumberInput'
      responses:
        '200':
          description: Default Response
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/SetPhoneAgentCallerNumberOutput'
        '500':
          description: Internal Server Error
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorDto'
components:
  schemas:
    SetPhoneAgentCallerNumberInput:
      $schema: https://json-schema.org/draft/2020-12/schema
      $id: '#/components/schemas/SetPhoneAgentCallerNumberInputInput'
      type: object
      properties:
        caller_number:
          anyOf:
            - type: string
              minLength: 1
            - type: 'null'
          description: >-
            A phone number verified in your workspace (E.164), or null to clear
            the caller ID. Clears the agent’s pool selection and keeps its
            assigned SIP trunk.
      required:
        - caller_number
    SetPhoneAgentCallerNumberOutput:
      $schema: https://json-schema.org/draft/2020-12/schema
      $id: '#/components/schemas/SetPhoneAgentCallerNumberOutput'
      type: object
      properties:
        phone_agent_id:
          type: string
        caller_number:
          anyOf:
            - type: string
            - type: 'null'
      required:
        - phone_agent_id
        - caller_number
      additionalProperties: false
    ErrorDto:
      type: object
      properties:
        statusCode:
          type: integer
        message:
          type: string
        error:
          type: string
  securitySchemes:
    bearerAuth:
      type: http
      scheme: bearer
      bearerFormat: JWT

````

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