To display the subpages in drop down combo box, we can use the below code.
<?php
$children = wp_list_pages('depth=1&title_li=&child_of='.$post->ID.'&echo=0');
if ($children) { ?>
<select name="g_subpages">
<option value="#">--Select A Team:--</option>
<?php
$childrens=explode("\n",trim($children));
for($i=0;$i<count($childrens);$i++)
{
$g_page_title=strip_tags($childrens[$i]);
$g_page_id= wt_get_ID_by_page_title($g_page_title);
$permalink = get_permalink($g_page_id);
?>
<option value="<?php echo $permalink ?>"><?php echo $g_page_title; ?></option>
<?php
}
?>
</select>
<?php } ?>