List subcategories with loop

wp-list_subcategories

/* List categories of categories page */
function list_my_subcategories(){
  	$q_cat = get_query_var('cat');
  	$cat = get_category($q_cat);
  	$catid = $cat->cat_name;
  	/*get the parent*/
  	$q_parent = $cat->category_parent;
  	$parent = get_category($q_parent);
  	$parentid = $parent->cat_name;

  	$html .= '';

  	if ($cat) {
  		$subcategories =  get_categories('child_of='.$cat->cat_ID.'');
  		if ($subcategories) {
  			foreach ($subcategories as $q_subcat) {
  				$subcat = get_category($q_subcat);
  				$subcatname = $subcat->cat_name;
  				$subcatid = $subcat->cat_ID;
  				$subcatLink = get_permalink($subcat);

  				$html .= '<div class="span12 service_container">';
  				$html .= '<div class="row">';
  				$html .= '<div class="span12 blueBackground product_block">';
  				$html .= '<h2 class="product_name_title">'.$subcatname;
  				$html .= '</h2>';
  				$html .= '</div>';
  				$html .= '<div class="span12 subCategoria">';
				$html .= '<div class="row subCategoriaFiltroCartucho">';

				global $post;
				$args = array('category_name' => $subcatname, 'post_type' => 'producto');
				$posts = get_posts($args);
				foreach ($posts as $post) : setup_postdata($post);
					$link  = get_permalink();
					$title = get_the_title();
					
					$html .= '<div class="span4 blueBackground service_name">';
					$html .= '<a href="'.$link.'">';
					$html .= '<h2 class="product_name_title">'.$title;
					$html .= '</h2>';
					$html .= '</a>';
					$html .= '</div>';
					
				endforeach;

				$html .= '</div>';
				$html .= '</div>';
				$html .= '</div></div>';

  			}
  		}
  	}


  	$html .= '';
  	return $html; 
}