Run every 5 minutes:
/usr/local/bin/php /home/YOURUSER/public_html/kq_isp_billing_saas/cron/expire_customers.php >/dev/null 2>&1

Optional radius accounting import every 15 minutes:
/usr/local/bin/php /home/YOURUSER/public_html/kq_isp_billing_saas/cron/import_radius_accounting.php >/dev/null 2>&1