AppointRequest with SOAP message to MS Dynamics CRM 4.0

I want to execute an AppointmentRequest through a SOAP message to Dynamics CRM 4.0 The following SOAP message I am posting:

<?xml version="1.0" encoding="utf-8"?>
<soap:Envelope xmlns:m0="http://schemas.microsoft.com/crm/2007/CoreTypes" xmlns:m="http://schemas.microsoft.com/crm/2007/WebServices" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
  <soap:Header>
    <m:CrmAuthenticationToken>
      <m0:AuthenticationType>0</m0:AuthenticationType>
      <m0:OrganizationName>MyOrg</m0:OrganizationName>
      <m0:CallerId>4d6792b2-d96f-de11-bc90-005056a243de</m0:CallerId>
    </m:CrmAuthenticationToken>
  </soap:Header>
  <soap:Body>
    <m:Execute>
      <m:request xsi:type="SearchRequest">
        <AppointmentRequest>
          <ServiceId>7b94C2A1D8-C201-DE11-B7B1-0022640DEB74</ServiceId>
        </AppointmentRequest>
      </m:request>
    </m:Execute>
  </soap:Body>
</soap:Envelope>

I am receiving back an error from CRM :

<?xml version="1.0" encoding="utf-8"?><soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2开发者_运维知识库001/XMLSchema"><soap:Body><soap:Fault><faultcode>soap:Server</faultcode><faultstring>Server was unable to process request.</faultstring><detail><error>
  <code>0x80040203</code>
  <description>request</description>
  <type>Platform</type>
</error></detail></soap:Fault></soap:Body></soap:Envelope>

Anyone with experience on this? I would be very thankfull if someone can help me or gives me tips

Thank you!

The error code 0x80040203 means InvalidArgument. See the list of Error Codes.

Enable the tracing (See How to enable tracing in Microsoft Dynamics CRM) which should give you more information about what's going wrong.