To prevent old order numbers getting updated while changing order status - By WebToffee (Sequential Order Number for WooCommerce Free)

functions.php

<?php //Do not copy this line of code

add_action('init', 'remove_order_status_changed_order_number', 15);

function remove_order_status_changed_order_number() {
    if (class_exists('Wt_Advanced_Order_Number')) {
        foreach ($GLOBALS['wp_filter']['woocommerce_order_status_changed']->callbacks as $priority => $hooks) {
            foreach ($hooks as $hook_id => $hook) {
                if (is_array($hook['function']) && is_object($hook['function'][0])) {
                    $object = $hook['function'][0];
                    if (get_class($object) === 'Wt_Advanced_Order_Number') {
                        remove_action('woocommerce_order_status_changed', array($object, 'wt_seq_order_status_changed'), 10, 4);
                    }
                }
            }
        }
    }
}