Restful services - unexpected change of parameter types

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C#

Hey there,
i am new to restful services.

I have a piece of code in 'ServiceContract' interface:

[OperationContract]
[WebInvoke(UriTemplate = "/NewUser")]
bool CreateNewUser(UserFullInfo newUser);

is exposed good at service reference as:

CreateNewUser(DoDoodles.DoodleService.UserFullInfo)

but if i change it to

[OperationContract]
[WebInvoke(UriTemplate = "/NewUser")]
UserCreateStatus CreateNewUser(UserFullInfo newUser);

where UserCreateStatus is enum (DataContract) service reference definition for the same changes to:

CreateNewUser(DoDoodles.DoodleService.CreateNewUserRequest request)

where is this CreateNewUserRequest coming from and why is it changed?
How can i rectify this and use the UserFullInfo object in a simpler way?

Thanks in advance!!