function update_post( $post_id ) {
   $post = array(
     'ID'         => $post_id,
     'post_title' => '#'.$post_id,
     'post_name'  => $post_id,
   );
   wp_update_post( $post );
   update_post_meta($post_id, 'order', $post_id);
}
add_action('save_post_booking', 'update_post', 20);