I think there is some service which Cisco sells, but can't remember what it's called. The big vendor is Empirix, but they are expensvie, but they can do pretty much any type of testing phone lines, data, email, etc. What I recommend, specially if you're trying to test an application with web services, is maybe increase the amount of calls your application makes and send it multiple calls on your own. It will never be enough, but it might help a bit.
david
