Unifaun - PreNOT

functions.php

<?php
/**
 * @snippet       WooCommerce - Adds ADDON to Shipment
 * @author        Redlight Media AB / Christopher Hedqvist
 * @compatible    WooCommerce 4.2.0
 */
function redlight_unifaun_prenot( $shipment, $order ) {
    // Only PUA and 'Varubrev - Lämnas vid dörr'
    if( 'P19' === $shipment['service']['id'] ){
        $shipment['service']['addons'][] = array(
            'id' => 'PRENOT'
        );
    }
  return $shipment;
}
add_filter('ac_wc_unifaun_shipment_data', 'redlight_unifaun_prenot', 10, 2 );