Phone switches may hit hang-ups:

"Like many people, Esparza has been comparison-shopping, trying to finagle the best deal from either T-Mobile USA Inc. or Verizon Wireless, his two top choices.

Deals are a key part of the game plan for wireless companies, as they try to retain old customers and woo new ones. Already, nearly a third of the 150 million Americans who have cell phones switch carriers every year. Analysts say that could increase to 40 percent under the new rules. So carriers are upping their offers, in the form of extra minutes, free talk time, cash credits and discounted phones."

AT&T, Cingular, Nextel will probably see the largest number of users change to different plans b/c of bad service, poor reception, or expensive plans.