public function toXMLString()
{
$str = '';
$str .= '<ns:BillOutstandingAmountReq>';
if ($this->BillOutstandingAmountRequest != null) {
$str .= '<ns:BillOutstandingAmountRequest>';
$str .= $this->BillOutstandingAmountRequest->toXMLString();
$str .= '</ns:BillOutstandingAmountRequest>';
}
$str .= '</ns:BillOutstandingAmountReq>';
return $str;
}
