The new iPhone 4 and iPad 3G model both use similar micro-SIM cards to access wireless data networks. Many users who own both devices are unhappy at being charged twice by AT&T. While this technique does work, it is not approved by AT&T, so please proceed at your own risk. HowToFixiPad.com is not liable for any damages or problems you may incur.
Use the micro-SIM tool to remove the card and cradle from both the iPhone and iPad. The cradles are not interchangeable, so be sure to keep them separate, and place the iPhone 4 micro-SIM and iPad cradle into the iPad.
Using the settings App, re-enable Cellular Data and double-check that the signal bars are displayed in the top left corner.
Now you must change the APN settings. Generally, these are configured automatically, but with the iPhone micro-SIM they must be entered manually.
APN Name: wap.cingular
Exit the Settings App and launch Safari to test the connection. If you can access a page, everything is functioning properly and you can take pride in your savings and circumventing AT&T’s data plan charges.