class ShippingItemType extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder
            ->addEventListener(FormEvents::PRE_SET_DATA, function ($event) use ($app) {
                $form
                    ->add('delivery', 'entity', array(
                        'class' => 'Eccube\Entity\Delivery',
                        'property' => 'name',
                        'choices' => $deliveries,        // ★変更したい選択肢
                        'data' => $delivery,
                        'constraints' => array(
                            new Assert\NotBlank(),
                        ),
                    ));
            })
    }

# 注文内容確認
front.shopping.index.initialize:
    - [onFrontShoppingIndexInitialize, NORMAL]

    /**
     * フロント画面：注文内容確認ページで配送方法を変更
     *
     * @param EventArgs $event
     */
    public function onFrontShoppingIndexInitialize(EventArgs $event)
    {
        $app = $this->app;
        if ($app->isGranted('ROLE_ADMIN')) {
            return;
        }

        $builder = $event->getArgument('builder');
        if (empty($builder)) {
            return;
        }
        $Order = $event->getArgument('Order');
        if (empty($Order)) {
            return;
        }

        $form = $builder->getForm();
        $Shippings = $form->get('shippings')->getData();
        if (!empty($Shippings)) {
            foreach ($Shippings as $key => $Shipping) {
                $Delivery = $Shipping->getDelivery();
                if ($Delivery) {
                  // ★choicesを変えたい
                }
            }
        }