problem changing the language

[eluser]keevitaja[/eluser]
now i have problem with languages.

Code:

<?php
class Subtest extends Controller {
  function index() {
    echo $this->config->item('language').'<br>'; //prints estonian, set in config file, default
    $this->config->set_item('language', 'english');
    echo $this->config->item('language').'<br>'; //prints english
    echo $this->lang->line('site_select_language'); //still prints out the estonian version
  }
}

i have both estonian and english versions in language folder
isn't it possible to change the language like that?

however if i change the config file and set $config['language'] = "english"; it will print out the english version!