Oracle XML xpath get value of current node in loop

This is my XML returned from the URL I call

<?xml version="1.0" encoding="ISO-8859-1"?>
<xml_calls>
    <calls ip="46.32.238.33">1038791</calls>
    <calls ip="212.44.61.2">3</calls>
    <calls ip="81.86.144.86">2</calls>
</xml_calls>

and this is my code I call to parse the XML

declare
    doc     xmldom.DOMDocument;

    data_list   xmldom.DOMNodeList;
    data        xmldom.DOMNode;

    Line_node_list  xmldom.DOMNodeList;
    Line_node       xmldom.DOMNode;
begin

    doc := xml.parseURL('http:// .... url to my xml doc ....');

    data_list := xpath.selectNodes(doc, '//xml_calls');
    data := xmldom.item(data_list, 0); -- node list index is zero based

   -- open the line_no node
    Line_node_list := xpath.selectNodes(data, './calls');

    for i in 1 .. xmldom.getLength(Line_node_list) loop
        Line_node := xmldom.item(Line_node_list, i-1);  

        dbms_output.put_line(xpath.valueOf(Line_node, './calls'));
        dbms_output.put_line(xpath.valueOf(Line_node, './@ip'));

    end loop;
end;

how can I get the value of the current node in the loop, ie the value of "calls" as in the loop xpath.valueOf(Line_node, './calls') returns null. Outside of the loop obviously it just returns the first value, 1038791

Am I missing something?

Thanks