Hi there,
I seems that the index file (index.php or index.html) is not in any way related to wordpress. As you say, it is a default page from you hostcompany.
First off, i think there is also a index.html file in your root directory, if so delete that file.
Make sure there is a index.php in your root directory which contains following code:
<?php
/**
* Front to the WordPress application. This file doesn't do anything, but loads
* wp-blog-header.php which does and tells WordPress to load the theme.
*
* @package WordPress
*/
/**
* Tells WordPress to load the WordPress theme and output it.
*
* @var bool
*/
define('WP_USE_THEMES', true);
/** Loads the WordPress Environment and Template */
require('./wp-blog-header.php');
?>
If that code isn't in the file than copy above into the index.php