email_processing_to_cancelled.php

<?php
/*
* Notification on order processing to cancelled status change
*/

function ci_cancelled_notification( $order_id ) {
 
    $order = wc_get_order( $order_id );
 
    // load the mailer class
    $mailer = WC()->mailer();
 
    $recipient = '[email protected]';
    $subject = __('Your Subject', 'codeinform');
    $content = ci_get_cancelled_notification_content( $order, $subject, $mailer );
    $headers = "Content-Type: text/html\r\n";
 
    $mailer->send( $recipient, $subject, $content, $headers );
 
}
 
add_action( 'woocommerce_order_status_processing_to_cancelled_notification', 'ci_cancelled_notification', 10, 1 );

function ci_get_cancelled_notification_content( $order, $heading = false, $mailer ) {
 
    $template = 'emails/admin-cancelled-order.php';
 
    return wc_get_template_html( $template, array(
        'order'         => $order,
        'email_heading' => $heading,
        'sent_to_admin' => true,
        'plain_text'    => false,
        'email'         => $mailer
    ) );
}