Access to related models in Forms

I have 2 tables in database:

class Customers extends \Phalcon\Mvc\Model
{
    public $id;
    public $name;
    public $lastname;

 public function initialize()
    {
        $this->setSchema("public");
        $this->hasMany('id', 'Customersactivation', 'cid', array('alias' => 'Customersactivation'));
    }
}

class Customersactivation extends \Phalcon\Mvc\Model
{
    public $id;
    public $cid;
    public $conbox;
    public $cablein;

public function initialize()
    {
        $this->setSchema("public");
        $this->belongsTo('cid', 'Customers', 'id', array('alias' => 'Customers'));
    }
}

My edit action:

 public function editAction($id)
    {
        if (!$this->request->isPost()) {

            $customer = Customers::findFirstById($id);
            if (!$customer) {
                $this->flash->error("Nie znaleziono klienta o id= $id");
                return $this->forward("customersactivation/index");
            }

            $this->view->form = new CustomersactivationForm($customer, array('edit' => true));
        }
    }

Form:

class CustomersactivationForm extends Form{

    public function initialize($entity = null, $options = array())
    {

        if (!isset($options['edit'])) {
            $element = new Text("id");
            $this->add($element->setLabel("Id"));
        } else {
            $this->add(new Hidden("id"));
        }

        $name = new Text("name");

        $name->setFilters(array('striptags', 'string'));
        $name->addValidators(array(
            new PresenceOf(array(
                'message' => 'Name is required'
            ))
        ));
        $this->add($name);

        $lastname = new Text("lastname");
        $lastname->addValidators(array(
            new PresenceOf(array(
                'message' => 'Lastname is required'
            ))
        ));
        $this->add($lastname);

    }
} 

How to get values from second table inside that Form?