Unless you're telling me the text message, minutes, and data usage numbers on my bill are all made up, I'm pretty sure the carriers have a way to track whose phone belongs to who. Or, if they can't provide a working opt-out, it should be opt-in only (using the cookie).
It can't really be opt-in using the cookie, as nobody should be touching any cookies in the process of a DNS lookup. Otherwise I agree completely; the carrier obviously knows that this is my phone or they couldn't tell me how much data I'm using.
