Error XmlException prefix ont is not defined

Hi all,

I'm creating an interface with an external application for updating sales orders in NAV.
I have created a page based on table 37 (Sales Line) with these fields:

- document type
- document no
- line no
- type
- no
- quantity

and published the page as a webservice.
I can reach the webservice thru my browser at http://monaco:7047/DynamicsNAV/WS/Page/ ... OrderLines.

When i load this webservice in SOAPUI it gives me this xml message for method Update:

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/&quot; xmlns:ont="urn:microsoft-dynamics-schemas/page/UpdateSalesOrderLines">
<soapenv:Header/>
<soapenv:Body>
<ont:Update>
<ont:UpdateSalesOrderLines>
<!--Optional:-->
<ont:Key>?</ont:Key>
<!--Optional:-->
<ont:Document_Type>?</ont:Document_Type>
<!--Optional:-->
<ont:Document_No>?</ont:Document_No>
<!--Optional:-->
<ont:Line_No>?</ont:Line_No>
<!--Optional:-->
<ont:Type>?</ont:Type>
<!--Optional:-->
<ont:No>?</ont:No>
<!--Optional:-->
<ont:Quantity>?</ont:Quantity>
</ont:UpdateSalesOrderLines>
</ont:Update>
</soapenv:Body>
</soapenv:Envelope>

Next i created a testfunction in NAV where i send this message

<?xml version="1.0" encoding="utf-8"?>
<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/"&gt;
<soap:Body>
<ont:Update>
<ont:UpdateSalesOrderLines xmlns="urn:microsoft-dynamics-schemas/page/UpdateSalesOrderLines>
<ont:Key></ont:Key>
<ont:Document_Type>1</ont:Document_Type>
<ont:Document_No>SO10-00562</ont:Document_No>
<ont:Line_No>10000</ont:Line_No>
<ont:Type>2</ont:Type>
<ont:No>1000</ont:No>
<ont:Quantity>10</ont:Quantity>
</ont:UpdateSalesOrderLines>
</ont:Update>
</soap:Body>
</soap:Envelope>

to the pagewebservice. Now when i execute this function it shows the following error:

1:System.Xml.XmlExeptionThe prefix ont is not defined.
Line 1, position 131. The prefix ont is not defined.

Can anyone explain this error and (better yet ;-)) provide a solution? [-o<

Thanx and

Best Regards