install.xml

<?xml version="1.0" encoding="utf-8"?>
<modification>
    <code>cdek-official</code>
    <name>CDEK Shipping Official</name>
    <version>dev</version>
    <author>CDEK IT</author>
    <link>https://www.cdek.ru/ru/integration</link>
    <file path="catalog/controller/checkout/simplecheckout_shipping.php">
        <operation>
            <search>
                <![CDATA[private function validator($shippingMethod) {]]>
            </search>
            <add position="after">
                <![CDATA[        $explodedShippingMethod = explode('.', $shippingMethod);

        if (($explodedShippingMethod[0] === 'cdek_official') && empty($this->session->data['cdek_office_code']) &&
            explode('_', $explodedShippingMethod[1])[0] === 'office') {
             $this->load->language('extension/shipping/cdek_official');
             return $this->language->get('cdek_pvz_not_found');
        }]]>
            </add>
        </operation>
    </file>
</modification>