Problem Using XML Web Service

[Skittle]

I'm trying to use a free xml web service. I have never done this before. The problem is that when I try to access the web service I get the error message:-

'System.Net.WebException:
The underlying connection was closed: Unable to connect to the remote server'

I've had a look around the web and it seems to relate to a proxy or firewall. The only information I have been able o find indicating how to get round the problem is to add the following code to my web.config:-

<system.net>
<defaultProxy>
<proxy
usesystemdefault="false"
bypassonlocal="false"
proxyaddress="

http://proxy.mycompany.com:myport";

/>
</defaultProxy>
</system.net>

The http address and port number are filled in to match the settings from my browser. Trouble is I then get a dialogue box error in .Net saying:-

'Error while trying to run project: Unable to start debugging on the Web Server. Server side-error occurred on sending Http request.'

I am trying to use the free XML service at:-

https://secure.cdyne.com/creditcardverify/luhnchecker.asmx?op=CheckCC

Any help would be greatly appreciated as I am at a bit of a loss as to where to go from here.

Dazed and confused