custom field not working not calling

hi i have next code in functions php and dont get result in email
when i call [suma]
//////////////////////////////////////////////////
function add_suma_to_cf7()
{
$html = ‘<input text name=”suma”>’;
$custom_fields = get_post_custom(get_the_ID());
foreach(@$custom_fields[‘amount’] as $total)
echo $html .= $total;
$html .='</text>’;
}
add_shortcode(‘suma’, ‘add_suma_to_cf7’);

https://www.ads-software.com/plugins/contact-form-7-modules/