form under inner form is not valid so you can use JavaScript function to load page
<script type="text/javascript">
function changestatus(value)
{
window.location.href="actionurl.php?sendvalue="+value;
}
</script>
call this function onchange event of select box like this
<form id="deleteSelected">
<table>
<tr>
<td><input type="checkbox" name="deleteSelected[]"/></td>
<td>Id</td>
<td>Name</td>
<td>Phone</td>
<td>
<!-- <form id="changeStatus">-->
<select name="item_id" onchange="changestatus(this.value);">
<option value="option1">option1</option>
<option value="option2">option2</option>
<option value="option3">option3</option>
</select>
<!-- </form>-->
</td>
</tr>
<table>
</form>
<script type="text/javascript">
function changestatus(value)
{
window.location.href="actionurl.php?sendvalue="+value;
}
</script>