To be able to talk with the webservice you'll need a proxy class. Of course
if all of your services implement the same interface, creating web
references using vs will result in "similar" proxy classes. Of course what
you want is not to create all these proxies from the beginning but instead
to be able to dinamically switch between services without creating a proxy
for it inthe first place.
What you have to do is manually create some sort of universal proxy, by
sneak-peaking at what VS is generating for one of your services. If all is
done right this universal proxy should be able to "talk" with any of your
services. At runtime you'll just have to make one instance of this proxy,
set its url to the desired webservice and start calling remote functions.

HTH