SOAP envelope xmlelement directcast not working

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VB

XML

SOAP

I'm successfully consuming a web-service SOAP envelope XML response. I've included a shortened version at the bottom.

(#1) when I use:

Dim totalcost1 As String = cfnroot.SelectNodes("GetRateQuoteResponse/GetRateQuoteResult/TotalCharges").Item(0).InnerText

I'm getting a value of 2597.01 which is correct.
(#2) When I use:

im totalcost As XmlElement = DirectCast(CFLxmldoc.SelectSingleNode("df:GetRateQuoteResponse/df:GetRateQuoteResult/df:TotalCharges", mgr), XmlElement)

I'm not getting a value at all.
I prefer to use #2's syntax and always have used it. I can't figure out why i'm not getting any value from #2. I find it easier to test for empty values or nodes that aren't present. This is my first time using a SOAP XML envelope. Normally use REST/URL.

<?xml version="1.0"?>
<SOAP-ENV:Body xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/">
  <GetRateQuoteResponse	xmlns="">
    <GetRateQuoteResult>
      <Date>03/22/2019</Date>
      <Time>12:06:22</Time>
      <DeficitAmount>152.84</DeficitAmount>
      <TotalCharges>2597.01</TotalCharges>
      <NetCharges>918.91</NetCharges>
     </GetRateQuoteResult>
  </GetRateQuoteResponse>
</SOAP-ENV:Body>

What I have tried:

Dim CFLresponse = CFLService.GetRateQuoteXml(CFLRaterequest)
Dim ResponseXML As String = CFLresponse.InnerXml
Dim CFLxmldoc As XmlDocument = New XmlDocument
CFLxmldoc.LoadXml(ResponseXML)

    Dim mgr As New XmlNamespaceManager(CFLxmldoc.NameTable)
mgr.AddNamespace("df", CFLxmldoc.DocumentElement.NamespaceURI)
Dim cfnroot As XmlElement = CFLxmldoc.DocumentElement

Dim totalcost As XmlElement = DirectCast(CFLxmldoc.SelectSingleNode("df:GetRateQuoteResponse/df:GetRateQuoteResult/df:TotalCharges", mgr), XmlElement)

Dim totalcost1 As String = cfnroot.SelectNodes("GetRateQuoteResponse/GetRateQuoteResult/TotalCharges").Item(0).InnerText