 Apple released the iPhone in the United States with a software " lock " so it could only be used on the AT & T Mobility network . After purchase , buyers activated their iPhone 's AT & T service contract using the Apple iTunes software , during which buyers had the ability to choose their billing preference ; however , if no option was specified during activation , AT & T defaulted to detailed billing . Detailed billing itemized every data transfer , including background traffic for e @-@ mail , text messaging , and Web browsing . This generated a large number of entries on the detailed bills . 
