When creating a new request via SOAP Web Services using the web services method "CreateRequest", one can name a category which is not meant for a request ticket (it is meant for incident or problem ticket types only)
Similar actions taken in the standard web UI will disallow an end user from selecting such a category per the settings in the category entry's cr_flag, in_flag and pr_flag field definitions
Release 17.4 GA - RU1
CA Service Desk Manager
Known issue in earlier builds of Service Desk 17.4, up until RU2
Issue will be addressed in 17.4 RU2 and later. RU update will also address a similar situation with REST web services as well.
A similar problem with the type field in a new request ticket is not being processed correctly will be addressed in 17.4 RU3
See the following KB Article for an example SOAP web services call on how to create a ticket using CreateRequest