// modifys contact form 7's default select value of --- to Please select...
function my_wpcf7_form_elements($html) {
	$text = 'Please select...';
	$html = str_replace('<option value="">---</option>', '<option value="">' . $text . '</option>', $html);
	return $html;
}
add_filter('wpcf7_form_elements', 'my_wpcf7_form_elements');