XSL File

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/">

  <xsl:output method="xml" indent="yes" />

  <xsl:template match="/">
    <xsl:for-each-group select="soapenv:Envelope/soapenv:Body/csv-set/csv-record" group-by="customer_id">
      <tims:Payload>
        <customer id="{customer_id}">
          <xsl:for-each select="current-group()">
            <value>{value}</value>
          </xsl:for-each>
        </customer>
      </tims:Payload>
    </xsl:for-each-group>
  </xsl:template>

</xsl:stylesheet>