How to prevent upload of a multiple sizes of images

I believe those are probably generated by the default WordPress sizes – thumbnail, medium and large. (See Appearance > Media for where those sizes are set).

If you want to eliminate the extra image sizes the simplest way might be to eliminate some of your theme’s custom image sizes and use the defaults instead. OR, you can “unset” the defaults. This article explains how to do that, but to sum up here’s the code you’d add to your theme’s functions.php file:

/**
 * Remove standard image sizes so that these sizes are not
 * created during the Media Upload process
 *
 * Tested with WP 3.2.1
 *
 * Hooked to intermediate_image_sizes_advanced filter
 * See wp_generate_attachment_metadata( $attachment_id, $file ) in wp-admin/includes/image.php
 *
 * @param $sizes, array of default and added image sizes
 * @return $sizes, modified array of image sizes
 * @author Ade Walker http://www.studiograsshopper.ch
 */
function sgr_filter_image_sizes( $sizes) {

    unset( $sizes['thumbnail']);
    unset( $sizes['medium']);
    unset( $sizes['large']);

    return $sizes;
}
add_filter('intermediate_image_sizes_advanced', 'sgr_filter_image_sizes');

Hope this helps, best of luck!