<?php

namespace Customize\EventListener\Mypage;

...

class ChangeEvent implements EventSubscriberInterface
{
    public static function getSubscribedEvents()
    {
        return [
            'Mypage/change.twig' => 'onRenderMypageChange',
        ];
    }

    /**
     * @param TemplateEvent $event
     */
    public function onRenderMypageChange(TemplateEvent $event)
    {
        $parameters = $event->getParameters();
        /** @var Customer $Customer */
        $Customer = ?????
    }
}