is_category not working

I’m using wordpress version 2.86 and I’m having problems with the “is_category” in php. What I’m trying to do is redirect a user to a page if the user clicks on a category. This is the code I tried:

<?php
 if (is_category('twitter')) {
 get_page($twitter-updates);
 }
?>

If this code is correct, then it says if the category “twitter” is displayed, then get/display the page “twitter updates”. When a user clicks on the category “twitter”, instead of displaying the posts in the category the browser will display the page “twitter updates”.