curl --request POST \
  --url https://{workspace}.spreesuite.com/billspree/users/account-config \
  --header 'Authorization: <api-key>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "method": "Retrieve",
  "action": "Fetch Hierarchies",
  "apiVersion": "v2"
}
'

{
  "success": true,
  "statusCode": 200,
  "message": "Request Succeeded.",
  "error": null,
  "data": [
    {
      "id": 5,
      "name": "Standard Hierarchy",
      "accounts": [
        {
          "id": 12,
          "accountName": "Region",
          "level": 1,
          "billingAccount": false
        },
        {
          "id": 13,
          "accountName": "Site",
          "level": 2,
          "billingAccount": false
        }
      ]
    }
  ]
}