Multiple webservice calls

I have a webservice (ASP.NET) deployed on a webfarm. A client application consumes it on daily basis. The problem is that some of its calls are duplicated (with difference of milliseconds). For example I have a function Foo(string a,string b). The client a开发者_如何学编程pp calls this webmethod as Foo('test1','test2') once but my log shows that it is being called twice or sometimes 3 or 4 times randomly. Is this anything wrong with the webfarm or the code? Note that the webmethod has simple straighfarward insert and update statements.

It seems that the issue will be with the webfarm. How do you identify the service? What is the end point looks like?