curl --request GET \
  --url https://api.cartesia.ai/agents/phone-numbers/{id} \
  --header 'Authorization: Bearer <token>' \
  --header 'Cartesia-Version: <cartesia-version>'

{
  "id": "<string>",
  "number": "<string>",
  "agent": {
    "id": "<string>",
    "name": "<string>"
  },
  "created_at": "2023-11-07T05:31:56Z",
  "updated_at": "2023-11-07T05:31:56Z",
  "provider": {
    "type": "twilio",
    "id": "<string>",
    "account_sid": "<string>",
    "api_key_sid": "<string>",
    "region": "us1"
  },
  "label": "<string>"
}