Woocomerce邮政编码在结帐页面选择框但ajax运输无法正常工作

Question

我在选择框中获得所有运输区域和固定费率组合的费用。但是当选择框更改值时，运费不起作用。

我在主题的文件功能中编写所有代码。这是我的代码：

// Hook in
   add_filter( 'woocommerce_checkout_fields' , 'vtnShipping' );

   function vtnShipping( $fields ) {
       $delivery_zones = WC_Shipping_Zones::get_zones();
       $vtnData['name'] = [];
       $vtnData['value'] = [];
       $vtnResults = [];
       foreach ( (array) $delivery_zones as $key => $the_zone ) {
         $vtnKhuVuc = $the_zone['zone_name'];
         $vtnTien = ($the_zone['zone_locations'][0]->type == 'postcode') ? $the_zone['zone_locations'][0]->code : $the_zone['zone_locations'][1]->code;

         array_push($vtnData['name'], $vtnKhuVuc);
         array_push($vtnData['value'], $vtnTien);
       }

       // Only
       foreach ($vtnData['value'] as $key => $value) {
          $vtnResults[$value] = $vtnData['name'][$key];
       }

       $fields['billing']['billing_postcode'] = array(
           'type'          => 'select',
           'class'         => array('billing_postcode'),
           'id'         => 'billing_postcode',
           'label'         => __('Nơi vận chuyển'),
           'required'    => true,
           'options'     => $vtnResults
    ); 

        return $fields;

   }

谢谢！