curl --request GET \
  --url https://your-instance.example.com/api/calls/providers/config \
  --header 'Authorization: Bearer <token>'

{
  "activeProvider": "sinch",
  "providers": [
    {
      "provider": "sinch",
      "isEnabled": true,
      "isConfigured": true,
      "phoneNumber": "+14165550100"
    }
  ],
  "userPhoneNumbers": [
    {
      "provider": "sinch",
      "phoneNumber": "+14165550100",
      "isDefault": true
    }
  ]
}