my radio button can't save to my database

Question

i have table 'a_installment' and the column is 'id' and 'nama', i try save to 'a_installment' using radio button with this code

etc/config.xml

<?xml version="1.0"?>
<config>
  <modules>
    <Veritrans_VtWebbni>
      <version>0.1.0</version>
    </Veritrans_VtWebbni>
  </modules>
  <global>
    <models>
      <vtwebbni>
        <class>Veritrans_Vtwebbni_Model</class>
        <resourceModel>veritrans_mysql4</resourceModel>
      </vtwebbni>
      <veritrans_mysql4>
        <class>Veritrans_Vtwebbni_Model_Mysql4</class>
        <entities>
          <vtwebbni>
            <table>a_installment</table>
          </vtwebbni>
        </entities>
      </veritrans_mysql4>
    </models>
    <resources>
      <veritrans_write>
        <connection>
          <use>core_write</use>
        </connection>
      </veritrans_write>
    </resources>
    <helpers>
      . . .
    </helpers>
    <blocks>
      . . .
    </blocks>
    <adminhtml>
      <layout>
        . . .
      </layout>
    </adminhtml>
  </global>
  <default>
    <payment>
      . . .
    </payment>
  </default>
  <frontend>
    <routers>
      . . .
    </routers>
  </frontend>
  <adminhtml>
    <layout>
      . . .
    </layout>
  </adminhtml>
</config>

Model/Vtwebbni.php

<?php
class Veritrans_Vtwebbni_Model_Vtwebbni extends Mage_Core_Model_Abstract
{
    public function _construct()
    {
        parent::_construct();
        $this->_init('veritrans/vtwebbni');
    }
}

Model/Mysql4/Vtwebbni.php

<?php
class Veritrans_Vtwebbni_Model_Mysql4_Vtwebbni extends Mage_Core_Model_Mysql4_Abstract
{
    public function _construct()
    {
        $this->_init('veritrans/vtwebbni', 'id');
    }
}

Model/Mysql4/Vtwebbni/Collection.php

<?php
class Veritrans_Vtwebbni_Model_Mysql4_Vtwebbni_Collection extends Mage_Core_Model_Mysql4_Collection_Abstract
{
    public function _construct()
    {
        parent::_construct();
        $this->_init('veritrans/vtwebbni');
    }
}

controllers/PaymentController.php

<?php

require_once(Mage::getBaseDir('lib') . '/veritrans-php/Veritrans.php');

class Veritrans_Vtwebbni_PaymentController
    extends Mage_Core_Controller_Front_Action {

  protected function _getCheckout() {
    return Mage::getSingleton('checkout/session');
  }

  public function redirectAction() { . . . }

  public function enable_payment(){ . . . }

  public function cancelAction() { . . . }

  public function convert_country_code( $country_code ) { . . . }
  public function saveAction()
  {
    //on recuperes les données envoyées en POST
    $nama = ''.$this->getRequest()->getPost('nama');
    //on verifie que les champs ne sont pas vide
    if(isset($nama)&&($nama!='') )
    {
      //on cree notre objet et on l'enregistre en base
      $contact = Mage::getModel('veritrans/vtwebbni');
      $contact->setData('nama', $nama);
      $contact->save();
    }
    //on redirige l’utilisateur vers la méthode index du controller indexController
    //de notre module <strong>test</strong>
    //$this->_redirect('#');
  }
}

?>

but my script don't work, no data record on my 'a_installment' table

sorry i forgot this

base/default/template/vtwebbni/form.phtml

<?php
$enable_payment = $this->getEnablePayment();
$direct_debit = $this->getDirectDebit();
$emoney = $this->getEmoney();
$cc =  $this->getCreditCard();
$bank_trans = $this->getBankTransfer();
$cstore = $this->getCstore();
?>

<style xmlns="http://www.w3.org/1999/html">. . .    </style>
<ul class="form-list" id="payment_form_<?php echo $this->getMethodCode() ?>" style="display:none;">
    <li>. . .    </li>
    <form action="<?php echo Mage::getUrl('vtwebbni/payment/save') ?>" method="post">
        <fieldset>
            <li class="control">
                <label class="required"><em>*</em><?php echo $this->__('BNI Installment') ?> </label></li>
            <li class="control">
                <label for="12">
                    <input type="radio" id="12" name="nama" class="input-radio validate-one-required-by-name" value="12" > <?php echo $this->__('12 month') ?>
                </label>
            </li>
            <li class="control">
                <label for="6">
                    <input type="radio" id="6" name="nama" class="input-radio  validate-one-required-by-name" value="6" > <?php echo $this->__('6 month') ?>
                </label>
            </li>
            <li class="control">
                <label for="3">
                    <input type="radio" id="3" name="nama" class="input-radio  validate-one-required-by-name" value="3" > <?php echo $this->__('3 month') ?>
                </label>
            </li>
            <li class="control">
                <label for="0">
                    <input type="radio" id="0" name="nama" class="input-radio  validate-one-required-by-name" value="0" checked> <?php echo $this->__('Full payment') ?>
                </label>
            </li>
            <li class="control"><input type="submit" value="Save" />
            </li>
        </fieldset>
    </form>
    <br>
</ul>

Answer 1

Replace bellow code in controllers/PaymentController.php

<?php
class Veritrans_Vtwebbni_PaymentController extends Mage_Core_Controller_Front_Action
{

  protected function _getCheckout()
  {
    return Mage::getSingleton('checkout/session');
  }

  public function redirectAction() { . . . }

  public function enable_payment(){ . . . }

  public function cancelAction() { . . . }

  public function convert_country_code( $country_code ) { . . . }

   public function saveAction()
   {
        //on recuperes les données envoyées en POST
        $nama = $this->getRequest()->getPost('nama',false);
        //on verifie que les champs ne sont pas vide
        if(isset($nama) && $nama) {
          //on cree notre objet et on l'enregistre en base
          $contact = Mage::getModel('veritrans/vtwebbni');
          $contact->setNama($nama);
          $contact->save();
        }
        //on redirige l’utilisateur vers la méthode index du controller indexController
        //de notre module <strong>test</strong>
        //$this->_redirect('#');
    }
}

?>