Not true. If you're a leaf node, the messaging traffic from ultrapeers should basically be zero, unless possibly you're sharing a TON of files. Exception: you may see a burst of traffic at first as the leaf and ultrapeer exchange some information.

Most likely your bandwidth is being used up by uploads and downloads. If that's not the case, perhaps you're an ultrapeer. You can check this by turning on the connections tab. If you don't want to be an ultrapeer, you can turn it off through Tools -> Options -> Speed.