IMSI stands for International Mobile Subscriber Identity; it is an identification code used to individually represent cell phones on the GSM and UMTS networks. IMSI is associated almost exclusively with Android-based cell phones, and is the functional equivalent to IMEI and MEID codes used across different cell networks to identify telephony-equipped electronic devices. Retrieving your IMSI is a fairly straightforward task regardless of the operating system your phone uses, and it should take no more than five minutes to learn and complete.
Using Android OS
Open the app drawer, then open the "Settings" app.
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Tap "About Phone" from the settings menu.
Tap "Status," then scroll down to the IMSI heading. Your IMSI number will be listed below this heading.
Using Symbian or Palm OS
Power up your phone.
Ensure that your phone has service, and that it is not in airplane mode.
Dial "*#06#" on the keypad, then press "Send." Your phone should display its IMSI number after a short delay.