"PHONE": [{"VALUE":$phone, "VALUE_TYPE":"WORK"}]

function make_field_contact($rec, $section, $value, $type)
{
        $res = [];
        $found = null;
        if (isset($rec) && array_key_exists($section, $rec) && is_array($rec[$section]))
        {
                foreach ($rec[$section] as $item)
                {
                        if (($item['VALUE'] == $value) && !$found) {
                                $res[] = ['ID'=>$item['ID'], 'VALUE'=>$value, 'VALUE_TYPE'=>$type];
                                $found = true;
                        } else {
                                $res[] = ['ID'=>$item['ID']];
                        }
                }
        }
        if (!$found) $res[] = ['VALUE'=>$value, 'VALUE_TYPE'=>$type];
        return $res;
}
...
$item['PHONE'] = make_field_contact($res['result'][0], 'PHONE', '79876543210', 'WORK');