The following lines were added (+) and removed (-):
An ESN is the '''E'''lectronic '''S'''erial '''N'''umber assigned to your iPhone and is used with CDMA phones. The ESN has been tied directly to the phones with CDMA carriers such as Verizon Wireless and Sprint. With the introduction of 4G service, a sim card has now been introduced, however, there remains an ESN tied directly to the phone itself in addition to a number on the sim card.