curl --request GET \
  --url https://api.voice.ai/agent/v1/agent/phone-numbers

{
  "phone_numbers": [
    {
      "phone_number": "<string>",
      "status": "<string>",
      "assigned_to_agent_id": "<string>",
      "assigned_to_agent_name": "<string>"
    }
  ],
  "total_numbers": 123,
  "total_available": 123,
  "total_assigned": 123
}