Multilevel XML to CSV XSLT transformation

I've been working on an XML to CSV transformation and I've been using the following XSLT doc for the transformation:

<?xml version="1.0"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://ift.tt/tCZ8VR">
  <xsl:output method="text"/>
  <xsl:variable name="delimiter" select="','"/>
  <xsl:key name="field" match="/*/*/*" use="local-name()"/>
  <xsl:variable name="allFields" select="/*/*/*[generate-id()=generate-id(key('field', local-name())[1])]"/>
  <xsl:template match="/">
    <xsl:for-each select="$allFields">
      <xsl:value-of select="local-name()"/>
      <xsl:if test="position() &lt; last()">
        <xsl:value-of select="$delimiter"/>
      </xsl:if>
    </xsl:for-each>
    <xsl:text/>
    <xsl:apply-templates select="*/*"/>
  </xsl:template>
  <xsl:template match="*">
    <xsl:variable name="this" select="."/>
    <xsl:for-each select="$allFields">
      <xsl:value-of select="$this/*[local-name() = local-name(current())]"/>
      <xsl:if test="position() &lt; last()">
        <xsl:value-of select="$delimiter"/>
      </xsl:if>
    </xsl:for-each>
    <xsl:text/>
  </xsl:template>
</xsl:stylesheet>

If I run the transformation on the following xml:

<?xml version="1.0"?>
<Calls>
  <Call xmlns="urn:eas-samples:en:xsd:phonecalls.1.0">
    <CustomerID>000391</CustomerID>
    <Filter1>1</Filter1> <Filter2>1</Filter2> 
  </Call>
  <Call xmlns="urn:eas-samples:en:xsd:phonecalls.1.0">
    <CustomerID>000528</CustomerID>
    <Filter1>1</Filter1> <Filter2>1</Filter2> 
  </Call>
</Calls>

The transformation works fine and I get the following result:

CustomerID,Filter1,Filter2
000391,1,1
000528,1,1

However if I add an additional level to the children, for example:

<?xml version="1.0"?>
<Calls>
  <Call xmlns="urn:eas-samples:en:xsd:phonecalls.1.0">
    <CustomerID>000391</CustomerID>
    <Filter1><AA>A</AA><BB>B</BB></Filter1>
  </Call>
  <Call xmlns="urn:eas-samples:en:xsd:phonecalls.1.0">
    <CustomerID>000528</CustomerID>        
    <Filter1>1</Filter1> <Filter2>1</Filter2> 
  </Call>
</Calls>

I get the following output:

CustomerID,Filter1,Filter2
000391,AB,
000528,1,1

The problem occurs no matter how many levels I end up adding. What I want is for all the child names and the values to be presented in a CSV fashion.

Any idea what I am doing wrong?

Thanks!