Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
On Verizon Wireless, you need consent of the account holder to separate from the plan. This could be via a phone call from a rep in a store.

Not sure how AT&T does it, but it couldn't hurt to have the primary account holder be expecting a phone call when you go in the store to do it.

(I would prefer to do this in store rather than online or on the phone)
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.