Server did not recognize the value of HTTP Header SOAPAction

This is a SOAP protocol exception. I got this exception when I tried to access a method in a webservice. The reason for getting this exception is that the method I accessed was not a web method.

The following is the exception that i recieved

soap:ClientSystem.Web.Services.Protocols.SoapException: Server did not recognize the value of HTTP Header SOAPAction: http://tempuri.org/GetFileString.
at System.Web.Services.Protocols.Soap11ServerProtocolHelper.RouteRequest()
at System.Web.Services.Protocols.SoapServerProtocol.RouteRequest(SoapServerMessage message)
at System.Web.Services.Protocols.SoapServerProtocol.Initialize()
at System.Web.Services.Protocols.ServerProtocolFactory.Create(Type type, HttpContext context, HttpRequest request, HttpResponse response, Boolean& abortProcessing)