Changing image in template Image Directory?

My header.php includes an image (called “phone” in the code below) that I’d like to change. I assume I could just delete and upload a new image in the theme image directory, but I can’t find my image directory anywhere.

<img src=”<?php bloginfo(‘template_directory’); ?>/images/phone.png” border=”0″ alt=”xxx” title=”xxx” class=”phone”>