Good Morning Shubha.
With my apology for miss-interpreting your question.
Further researching and testing for this, did not reveal a possible WSDL-method-implementation to accomplish what you ask for: Get the Request(_id)'s Service-Options listed.
You might consider to open an Idea for this?
Or see, whether other user(s) in the community, to further advise you on this subject.
Thanks for your understanding on this and kind regards, Louis.