Before proceeding you need a Jailbroken iPhone (any model, any baseband and any firmware) by any method, tethered, semi-tethered or untethered, the SIM you want to use with the iPhone already inserted and the last version of iTunes installed.
-Step 1: Add this repo to Cydia:
http://repo.bingner.com and search/install Sam Bingner's
SAM package.
-Step 2: Launch
SAMPrefs by clicking its icon.
-Step 3: Go to Utilities and select De-Activate iPhone. Check the More Information section to be sure.
-Step 4: In
Method, click on
By Country and Carrier Then select your original carrier. (The carrier who sold you the iPhone, not the SIM's you want to use). It may possible that you need to select SIM ID as well, so consider doing that if the procedure fails and the end of this guide.
-Step 5: Click on
More Information again and in
SAM Details copy the
IMSI number (International Mobile Subscriber Identity) that is showed there.
-Step 6: Click on
Spoof Real SIM to SAM.
-Step 7: Get back to SAM's main menu and change the Method to
manual. Paste or introduce the IMSI you copied before in the editable field.
-Step 8: Connect your iPhone to your computer and open iTunes to re-activate your phone, double click on "Phone Number" parameter at the main device screen in iTunes and check if the ICCID matches that of your SIM card (SAM shows you this). If not you need to get back to Step 1.
-Step 9: Unplug you iPhone and close iTunes.
-Step 10: Disable SAM in the SAMPrefs app.
-Step 11: Plug your iPhone to your computer again and open iTunes. It will tell you it can't activate the iPhone.
-Step 12: Close iTunes and open it again.
-Step 13: Wait patiently while iTunes activates your iPhone this time for real and... Voila! Unlocked!
-Final step: If your push notifications stopped working, open SAM again and click on
Clear Push and then connect to iTunes once more.