unitymedia doesn't provide usenet access for their customers.
for text articles, look for open nntp servers, e.g. from universities and not the provider one's. they are normally dedicated to their own customers.
if you're looking for binary articles, you have to use a chargable service like giganews, newshosting, eweka, ... and don't use german usenet reseller like usenext, alphaload, etc., because the pricing and contract conditions are horrible