User role based show/hide few methods in ASMX/WCF service?

Question

Hi,
Say for example I have an ASMX service or a WCF service with say 50 methods. Now, based on the user who is trying to access the web service, I would like to hide few methods.
Like for example, say a Level 1 user gets access to only 10 methods from the 50 methods, level 2 user gets access to 30 methods and a level 3 user gets access to all the methods.
Is this possible?
Or do I need to create separate web services for each level user?
Thanks!