Попробуйте также отключать поля для доставки ['shiping']
// remove shipping fields
unset($fields['shipping']['shipping_first_name']);
unset($fields['shipping']['shipping_last_name']);
unset($fields['shipping']['shipping_company']);
unset($fields['shipping']['shipping_address_1']);
unset($fields['shipping']['shipping_address_2']);
unset($fields['shipping']['shipping_city']);
unset($fields['shipping']['shipping_postcode']);
unset($fields['shipping']['shipping_country']);
unset($fields['shipping']['shipping_state']);
