Web Service MYProblem

I add to web reference for my cross platrom to two platform droid and ios .There tho reference is same. But I don't use to two platform. I add to ios web reference and droid web reference . I want to my device platform then ios using to ios web reference , then android using to droid web reference . How I do this? Can you help me ? Thanks!

Web Reference Droid Web Reference Ios