Hey Neha :)
Obviously it is a matter of approach, but in my opinion there should be just one
call method per service object. If you look at other paragraph related to naming recommendations, then it would make it much more clear. I.e. it makes no sense to create more than one method for
DestroyUser service, as the service name already defines the one and only responsibility.
DestroyUser.call(81) acts like a “global command” you can execute.
UserService on other hand does not communicate clearly what is possible to be do done with a user, and can become a code dump significantly violating rules like SRP.
So to answer your question, my subjective recommendation is: yes, one, public, standardised method per service.