Você fez perguntas muito parecidas. Peguei as informações de ambos e construí este exemplo de trabalho. Esteja ciente do namespace xmlns que deve ser declarado como "DEFAULT":
Simplifiquei seu XML, mas a ideia deve dar certo...
DECLARE @allUsers XML=
'<?xml version="1.0"?>
<?mso-application progid="Excel.Sheet"?>
<Workbook xmlns="urn:schemas-microsoft-com:office:spreadsheet"
xmlns:o="urn:schemas-microsoft-com:office:office"
xmlns:x="urn:schemas-microsoft-com:office:excel"
xmlns:ss="urn:schemas-microsoft-com:office:spreadsheet"
xmlns:html="http://www.w3.org/TR/REC-html40">
<Worksheet>
<Table>
<Row ss:AutoFitHeight="0" ss:Height="30">
<Cell ss:StyleID="s22"/>
<Cell ss:StyleID="s24"><Data ss:Type="String">Jane Doe</Data></Cell>
<Cell ss:StyleID="s24"><Data ss:Type="String">JaneDoe</Data></Cell>
<Cell ss:StyleID="s24"><Data ss:Type="String">XYZ</Data></Cell>
<Cell ss:StyleID="s24"><Data ss:Type="String">(555) 555-5555</Data></Cell>
<Cell ss:StyleID="s22"/>
</Row>
</Table>
</Worksheet>
</Workbook>';
;WITH XMLNAMESPACES ('urn:schemas-microsoft-com:office:spreadsheet' as ss
,DEFAULT 'urn:schemas-microsoft-com:office:spreadsheet')
SELECT T.X.value('Cell[1]/Data[1]','varchar(max)') AS DontKnow1
,T.X.value('Cell[2]/Data[1]','varchar(max)') AS Name
,T.X.value('Cell[3]/Data[1]','varchar(max)') AS UserName
,T.X.value('Cell[4]/Data[1]','varchar(max)') AS DontKnow2
,T.X.value('Cell[5]/Data[1]','varchar(max)') AS Telephone
,T.X.value('Cell[6]/Data[1]','varchar(max)') AS DontKnow3
FROM @allUsers.nodes('/Workbook/Worksheet/Table/Row') as T(X)
