Symfony2-How to use access a service from outside of a controller

In my Symfony2 controller, this works fine:

$uploadManager = $this->get('upload.upload_manager');

but when I move it to a custom Listener:

use Doctrine\ORM\Event\LifecycleEventArgs;
use Acme\UploadBundle\Upload\UploadManager;

class PersonChange
{
    public function postRemove(LifecycleEventArgs $args)
    {
        $entity = $args->getEntity();
        $entityManager = $args->getEntityManager();

        $uploadManager = $this->get('ep_upload.upload_manager');
        echo "the upload dir is " . $uploadManager->getUploadDir();
    }
}

I get an error:

Fatal error: Call to undefined method Acme\MainBundle\Listener\PersonChange::get() in /home/frank/...

I know I must need a use statement but don't know what to use.