how to call web service from C# .net windows app

I have a c# windows form.  I have added a web reference to a web service running on another server on my network.
I have verified that the web service is responding by using VisualWebServiceClient  (VWSC)(http://digitforge.com/Public/Downloads.aspx) (great utilility by the way).

VWSC shows me the request that it sends to the web service as being -
===================================================================
<?xml version="1.0" encoding="utf-8"?>
<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" xmlns:soapenc="http://schemas.xmlsoap.org/soap/encoding/" xmlns:tns="http://strongmail.com/soap/strongmail.wsdl" xmlns:types="http://strongmail.com/soap/strongmail.wsdl/encodedTypes" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
    <soap:Body
        soap:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/">
        <execute>
            <smIn
                xsi:type="xsd:string">&lt;strongmail-client username="admin" password="admin"
 context="clientinfo" action="mailings"&gt;
&lt;mailing&gt;
&lt;status code="3"&gt;Active&lt;/status&gt;
&lt;/mailing&gt;
&lt;/strongmail-client&gt;</smIn>
        </execute>
    </soap:Body>
</soap:Envelope>
===================================================================

My questinon is how do I call the same web service and pass it the same info from inside a C# windows app?

I have the following lines of code -
====================================================================
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using StrongMailWebServicesTest1.StrongMail;
using System.Xml;

namespace StrongMailWebServicesTest1
{
    public partial class Form1 : Form
    {
        strongmail sm = new strongmail();

        public Form1()
        {
            InitializeComponent();
        }
        private void button1_Click(object sender, EventArgs e)
        {
           
            smIn = "&lt;strongmail-client username=&quot;admin&quot; password=&quot;admin&quot; context=&quot;clientinfo&quot; action=&quot;mailings&quot;&gt;&lt;mailing&gt;&lt;status code=&quot;3&quot;&gt;Active&lt;/status&gt;&lt;/mailing&gt;&lt;/strongmail-client&gt;";
            string smOut = "";            
            smOut = sm.execute(smIn);          
        }
    }
}
====================================================================

But I get a response back (smOut) telling me that there was an error parsing the input.

Thanks,

Kevin.