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

{
  "type": "twilio",
  "id": "<string>",
  "account_sid": "<string>",
  "api_key_sid": "<string>",
  "region": "us1"
}