Server did not recognize SOAPAction

I have problems hosting a super simple asp xml service
sending a correct soap request, but keep getting

System.Web.Services.Protocols.SoapException: Server did not recognize the value of HTTP Header SOAPAction: http://www.quizmap.net/Add

the service is as follows:

<%@ WebService Language=C# class=MyClass %>

using System.Web.Services ;

public class MyClass
{
[WebMethod()]
public int Add ( int a, int b)
{
return a + b ;
}
}

Ive put the .asmx on root as well as under subfolders.
Im new to this , so guess there is something basic im missing out on

Could it be that my account at discountasp.net is not supporting this type of webservice?