Update: This only works until the TMSI is refreshed which means it won’t last very long

Michael Capozzi (via Chronic) has apparently discovered how to unlock the iPhone 4S (reportedly AT&T version only) without any software or hardware tweaking. The unlock will assist you in using your iPhone 4S on T-Mobile’s network as long as you have a T-Mobile SIM card. Before you get started, go ahead and cut down your T-Mobile SIM card to match your AT&T SIM card’s size. Go ahead and give the following directions a try:

  • Insert original carrier AT&T SIM card
  • Dial 611 for AT&T customer service hotline and drop the call
  • Turn on Airplane Mode
  • Take out AT&T SIM card
  • Insert T-Mobile SIM card

Update: the unlock also works with the iPhone 3GS and iPhone 4, and will need to be done again if you reset your device. Continue after the break..

6. Make sure WiFi is off ( also tap on ‘Forget this Network” to make sure it doesn’t connect automatically later)

  1. Switch off Airplane Mode and iPhone will search for network. This is followed by the Apple splash screen appearing.

  2. Activation Required will be displayed on the screen

  3. EDGE network will activate automatically – notice the ‘E’ on the top left corner of the screen

  4. Wait for about 20-30 seconds and turn off the phone

  5. Turn on iPhone and the same Activation Required screen will be displayed

  6. When you see one signal bar, tap on Use Cellular Connection

  7. Eject SIM card

  8. Activation Required screen will be displayed the second time

  9. Insert SIM card

  10. Unlocked!

If cutting down your SIM isn’t your thing you can obtain a microSIM through T-Mobile’s website.

  • Apple already selling unlocked, contract-free iPhone 4S in the United States (9to5mac.com)
  • Apple online store now accepting orders for unlocked iPhone 4S as Sprint begins SIM-locking them (9to5mac.com)
  • Simple Mobile micro SIM Card for iPhone for $1 + free shipping, more (9to5toys.com)