Telephone number for ordered SKU form List
getCollection()->addAttributeToSelect('*');
$ordersCollection->addAttributeToFilter('entity_id', array(
    'from' => 534533,
    'to' => null
));

$ordersProduct = array();
foreach ($ordersCollection as $o) {
    $items = $o->getAllVisibleItems();
    foreach ($items as $i) {
        $itemData = $i->getData();
        $sku = $itemData['sku'];
        if (isset($skuList[$sku])) {
            if (isset($itemData['product_id'])) {
                $phone = $o->getBillingAddress()->getTelephone();
                $phone = prepareTelephoneNumber($phone);
                $ordersProduct[$itemData['sku']][$phone] = [$phone];
            }
        }
    }
}
unset($ordersCollection);


$phoneList = [];
foreach ($ordersProduct as $key => $value) {
    foreach ($value as $key2 => $value2) {
        $phoneList[$key2] = $key2;
    }
}
unset($ordersProduct);

foreach ($phoneList as $value) {
    echo $value;
    echo '
';
}

die('');


function prepareTelephoneNumber($value)
{
    $value = preg_replace('/[^0-9]/', '', $value);
    if (strlen($value) == 10) {
        $value = '38' . $value;
    }

    return $value;
}