You probably already know about possibility to unlock your iPhone on any firmware version and any baseband using SAM unlock. It's really working method, and involves some skills like knowing IMSI number of your device. We will now try to explain what it is and where to find it. Let's start form the very beginning. Subscriber Identification Module (SIM) is a chip that stores:
  • International Mobile Subscriber Identity (IMSI)
  • ICCID - unique serial number
  • Security authentication and ciphering information
  • Info that is stored temporarily and sent to your local network
  • List of services available for user
  • Personal identification number (PIN)
  • Personal unblocking code (PUK)
How to Find IMSI Number 1
How it works: your iPhone sends IMSI number to the network while registering. IMSI number is exactly the thing that allows network hardware to identify the subscriber. To avoid the interception IMSI is sent as rarely as it is possible. Sometimes instead of IMSI the phone sends TMSI (temporarily generated code for mobile subscriber identity). How to Find IMSI Number 2 Be careful not to confuse IMSI and IMEI (which stands for International Mobile Equipment Identity - 15-digit number unique for every phone on GSM and UMTS). IMEI is also sent to the carrier by registering in network. IMEI can be easily used for tracking phones and blocking stolen ones on carrier level. So let's see, you know about SAM unlock, you've downloaded it and installed on your device but you're unable to find your IMSI (or don't know what it is at all), then just continue reading. IMSI is International Mobile Subscriber Identity - a unique SIM card number. This is NOT a feature or a function of your phone . It consists of  15 digits that can be splitted in three categories:
  • MCC (Mobile Country Code) - first three digits of IMSI code
  • MNC (Mobile Network Code) - fourth and fifth for EMEA countries (Europe, the Middle East and Africa) or fourth, fifth and sixth digits in the code for the other (NAR) countries
  • MSIN (Mobile Station Identification Number) - the last 9/10 digits of the code
How to Find IMSI Number 3

IMSI number for EMEA countries looks like this:

IMSI number EMEA

IMSI number for NAR countries:

IMSI number NAR The MCC and MNC digits from 1 to 5/6 (red and yellow on the images) show the network. Subsets and regional operators can be calculated by last 9 or 8 digits (blue and yellow) aka MSIN. Where is IMSI stored locally: all the IMSI bundles are stored in /System/Library/Carrier Bundles. For instance, if you use AT&T SIM card, his name will be ATT_US.bundle var/mobile/Library/Carrier Bundles. The iOS will also create shortcut to that folder which will look like this: var/mobile/Library/Carrier Bundle.bundle. How to Find IMSI Number 4 To find your iPhone's IMSI number you can use two methods. One is to check IMSI by running minicom in your terminal and typing in: AT+CIMI then press enter and you'll see your IMSI number. The second method fits SAM unlock better. Run installed SAM app on your iPhone and go to More Information->IMSI under SIM Details submenu. You'll see a 15-digit IMSI code that corresponds to your SIM card. That's it.

IMPORTANT! How to find your carrier within IMSI:

  • When you have that number just check iPhone operator
  • Type it in to the field called Enter IMSI number
  • It will show your SIM carrier's country, operator, your MCC and MNC
ATTENTION: If you've already detected your iPhone's IMSI (Country, carrier and Mobile Station Identificator Number) but it isn't listed in SAM's By Country and Carrier activation list, or know your IMSI number but don't know your carrier then check out my FULL IMSI list of international carriers to unlock iPhone with SAM. How to Find IMSI Number 5 How to enter your IMSI number to By Country and Carrier activation method: Let's say your IMSI is 234150829435109.  The digits stand for:
  • Carrier - 15 - VODAFONE LTD
  • SIM ID - 23415
More questions? Please comment below!
Update: Now you know the network to which your iPhone locked, so check this operators IMEI unlock list and find your carrier for free unlock!