Problem with (Page) Webservice Update

Hi,
I want to update a customer record via webservice.
I created a page containing no and name nad published it as a webservice.
I called the read and created an update there I set the key to the value form the read statement and a new customer name.
My problem ist that the customer record is not updated after calling the webservice.

the update statement looks like this:

<?xml version="1.0" encoding="utf-8"?>
<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" xmlns:wsc="urn:microsoft-dynamics-schemas/page/cust">
<soap:Body><wsc:Update>
<wsc:Key>25;EgAAAACJ/0RFOTg5OTY3OQ==11;63484732680;</wsc:Key>
<wsc:No>C00000001</wsc:No>
<wsc:Name>new name</wsc:Name>
</wsc:Update></soap:Body>
</soap:Envelope>

the result:

<Soap:Envelope xmlns:Soap="http://schemas.xmlsoap.org/soap/envelope/">
   <Soap:Body>
      <Update_Result xmlns="urn:microsoft-dynamics-schemas/page/cust"/>
   </Soap:Body>
</Soap:Envelope>