<?php
require_once "Mage/Customer/controllers/AccountController.php";
class User_Tracker_AccountController extends Mage_Customer_AccountController{

public function loginPostAction()
{
    if (!$this->_validateFormKey()) {
        $this->_redirect('*/*/');
        return;
    }

    if ($this->_getSession()->isLoggedIn()) {
        $this->_redirect('*/*/');
        return;
    }
    $session = $this->_getSession();

    if ($this->getRequest()->isPost()) {
        $login = $this->getRequest()->getPost('login');

   //added code

         $phoneNumber = $login['username'];
    $customer = Mage::getResourceModel('customer/customer')
        ->addAttributeToSelect('phone_number')
        ->addAttributeToFilter('phone_number', $phoneNumber)
        ->getFirstItem()->getCustomer();
    if ($customer !== false) {
        $login['username'] = $customer->getEmail();
    }else{
        $login['username'] = $phoneNumber;
    }

    //end here

        if (!empty($login['username']) && !empty($login['password'])) {
            try {
                $session->login($login['username'], $login['password']);
                if ($session->getCustomer()->getIsJustConfirmed()) {
                    $this->_welcomeCustomer($session->getCustomer(), true);
                }
            } catch (Mage_Core_Exception $e) {
                switch ($e->getCode()) {
                    case Mage_Customer_Model_Customer::EXCEPTION_EMAIL_NOT_CONFIRMED:
                        $value = $this->_getHelper('customer')->getEmailConfirmationUrl($login['username']);
                        $message = $this->_getHelper('customer')->__('This account is not confirmed. <a href="%s">Click here</a> to resend confirmation email.', $value);
                        break;
                    case Mage_Customer_Model_Customer::EXCEPTION_INVALID_EMAIL_OR_PASSWORD:
                        $message = $e->getMessage();
                        break;
                    default:
                        $message = $e->getMessage();
                }
                $session->addError($message);
                $session->setUsername($login['username']);
            } catch (Exception $e) {
                // Mage::logException($e); // PA DSS violation: this exception log can disclose customer password
            }
        } else {
            $session->addError($this->__('Login and password are required.'));
        }
    }

    $this->_loginPostRedirect();
}

<config>
...... // YOUR OTHER CODE
......
    <frontend>
        <routers>
            <customer>
                <args>
                    <modules>
                        <User_Tracker before="Mage_Customer">User_Tracker</User_Tracker>
                    </modules>
                </args>
            </customer>
        </routers>
    </frontend>
......
......
</config>

$phoneNumber = $login['username'];
$customer = Mage::getResourceModel('customer/customer_collection')
    ->addAttributeToSelect('phone_number')
    ->addAttributeToFilter('phone_number', $phoneNumber)
    ->getFirstItem();
if ($customer !== false) {
    $login['username'] = $customer->getEmail();
}else{
    $login['username'] = $phoneNumber;
}

if (strpos($login['username'], '@') === false){ //the user has entred a phone number
          $telUser = $login['username'];
          $customer = Mage::getModel('customer/customer')->getCollection()
                       ->addAttributeToFilter('phone_number', $telUser)
                       ->getFirstItem();
          if($telUser == $customer->getPhoneNumber()){
              $login['username'] = $customer->getEmail();
          }
    }