inserting data into database[help!]

[eluser]miwrath[/eluser]
can any one can correct this code please...

this is my registration model that should be inserting data into the db...

but unfortunately this error comes out:

Code:

( ! ) Fatal error: Call to undefined method User_reg::check_username_exists() in D:\wamp\www\registrar\system\application\controllers\registrar.php on line 62
Call Stack
#    Time    Memory    Function    Location
1    0.0011    381952    {main}( )    ..\index.php:0
2    0.0030    431568    require_once( 'D:\wamp\www\registrar\system\codeigniter\CodeIgniter.php' )    ..\index.php:115
3    0.1436    3040856    call_user_func_array ( )    ..\CodeIgniter.php:236
4    0.1436    3040904    Registrar->register( )    ..\CodeIgniter.php:0
5    0.1439    3048992    CI_Form_validation->run( )    ..\registrar.php:31
6    0.1456    3054376    CI_Form_validation->_execute( )    ..\Form_validation.php:337
7    0.1471    3055224    Registrar->username_not_exists( )    ..\Form_validation.php:589

here is my controller code:

Code:

function register()
        {
              
          
            $this->form_validation->set_rules('username', 'Username', 'trim|required|alpha_numeric|xss_clean|strtolower|callback_username_not_exists');
            $this->form_validation->set_rules('password', 'Password', 'trim|required|alpha_numeric|xss_clean');
            $this->form_validation->set_rules('password_conf', 'Password Confirmation', 'trim|required|alpha_numeric|xss_clean|matches[password]');
            $this->form_validation->set_rules('teach_id', 'ID Number', 'trim|required|alpha_numeric|min_length[10]|xss_clean');
            $this->form_validation->set_rules('f_name', 'First Name', 'trim|required|alpha_numeric|xss_clean');
            $this->form_validation->set_rules('m_name', 'Middle Name', 'trim|required|alpha_numeric|xss_clean');
            $this->form_validation->set_rules('l_name', 'Last Name', 'trim|required|alpha_numeric|xss_clean');
            $this->form_validation->set_rules('position', 'Position', 'trim|required|alpha_numeric|xss_clean');
            
            if ($this->form_validation->run() == FALSE)
            {
                 $this->load->view('register');
                
            }
            else
            {
                //everything is good!
                $username = $this->input->post('username');
                $password = $this->input->post('password');
                $password_conf = $this->input->post('password_conf');
                $teach_id = $this->input->post('teach_id');
                $f_name = $this->input->post('f_name');
                $m_name = $this->input->post('m_name');
                $l_name = $this->input->post('l_name');
                $position = $this->input->post('position');
                
                
                $this->User_reg->register_user($username, $password, $password_conf, $f_name, $m_name, $l_name, $teach_id, $position);
                
            }
            
            
          
        }

and this is my model for the registration:

Code:

<?php
class User_reg extends Model
{

function User_reg()
{
    parent::Model();
  
}

function register_user($username, $password, $password_conf, $f_name, $m_name, $l_name, $teach_id, $position)
{
   $sha1_password = sha1 ($password);
    
    $query_str = "INSERT INTO accnt_info (username,password,teach_id,f_name,m_name,l_name,position)
        VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)";
    
    $this->db->query($query_str, array($username, $sha1_password, $password_conf, $teach_id, $f_name, $m_name, $l_name, $position));
    
}


}