Although the Apple iPhone is only available on the AT&T network as of October 2010, customers can switch to T-Mobile without having to jailbreak their iPhone. Many customers are dissatisfied with AT&T due to its high prices and bad service. If you are an AT&T customer who is unhappy with the carrier, but wants to continue using the iPhone, or a T-Mobile customer who wants an iPhone, you can easily make the switch. T-Mobile has made their SIM cards so they fit in iPhones, so iPhone users can have T-Mobile service without buying a jailbroken iPhone.
Instructions
1. Purchase a T-Mobile SIM card, and activate it. SIM cards are sold at T-Mobile stores and online. You activate it over the phone or online, but make sure to select a smartphone plan.
2. Insert the end of a paper clip in the tiny hole in the SIM tray to release it. (The tray is located on the right side of the iPhone 4 and the top of the original, 3G and 3GS.)
3. Put the T-Mobile SIM card in the tray, and put it back in.
4. Turn on the iPhone, and press "Settings."
5. Tap "Off" next to "3G" on the "Network" page.
6. Tap "Cellular Data" on the "Network" page. Type "epc.tmobile.com" in the APN field, but leave the username and password blank. This will allow you to use the T-Mobile network rather than AT&T.
7. Press the "Home" button under the screen to exit "Settings."
Tags: Network page, switch T-Mobile, T-Mobile card