Its quite hard to answer your question without seeing your C# code and your exact configuration. Here are some ideas for you to try and check
- are you using http://myOTRSurl.com/nph-genericinterface.pl/Webservice/MyWebServiceName to access the webservice?
- Is there any debugging information in otrs. GO to 'Admin'->'Web Services' -> select the web service -> 'Debugger' -> view the request list for any information that can help you debug your specific problem
- Debug your C# code to make sure the soap message is formed correctly with the tags opened and closed.
- Go to the developer API for the ticketget http://dev.otrs.org/cvs/Kernel/GenericInterface/Operation/Ticket/TicketGet.html and http://dev.otrs.org/cvs/Kernel/GenericInterface/Operation/Ticket/TicketCreate.html are you providing the required parameters in the SOAP?
Hope this helps a bit. For more info you can read details in http://doc.otrs.org/3.2/en/html/genericinterface.html