I tried to create a client using the wsdl/xsd you posted and couldn't. The request parameter isn't defined.
wsdl regKasseService.wsdl regKasse.xsd regKasseService.
wsdl
Microsoft (R) Web Services Description Language Utility
[Microsoft (R) .NET Framework, Version 2.0.50727.3038]
Copyright (C) Microsoft Corporation. All rights reserved.
Error: Unable to import binding 'rkdbServiceBinding' from namespace 'https://fin
anzonline.bmf.gv.at/rkdb'.
- Unable to import operation 'rkdb'.
- The element 'https://finanzonline.bmf.gv.at/rkdb:rkdbRequest' is missing.
If you would like more help, please type "wsdl /?".
It sounds like you're trying to overload the web service method. SOAP doesn't support that. About the best you can do is create a declaration for each anticipated use and use a different MessageName on each one.