Your mobile's IMEI number -- short for International Mobile Equipment Identity -- is a 15- to 17-digit code unique to your mobile. This code does not change when you use a different SIM card. Theoretically, if you lose your phone, your mobile network can use your phone's IMEI code to locate it. The catch is you are unlikely to get much cooperation from your mobile network unless the police ask it to help. However, most mobile networks can use your IMEI number to block a stolen mobile phone so that thieves can't use it.
Find out what your IMEI number is. Enter "*#06# " on your phone's keypad. A 15- to 17-digit number will come up on the screen; write it down.
Contact your mobile network if your phone is stolen. Give the network your IMEI code and ask for help finding your phone. If you have good contacts in the company, or you have a great sob story to tell, the network may help you. This is unlikely. Regardless, ask customer support to block your phone and add it to the industry's black list. This will make your handset useless to the thief and increase your chances of recovering it.
Contact the police and report your stolen phone. Give the police your phone's IMEI number. Investigators can use it to identify the phone as yours if it is recovered. Also, If your mobile network will not cooperate with finding your phone, ask the police for help. Networks will cooperate if a law enforcement agency requests it. However, the police generally only will take the time to track a phone when it is related to more serious crimes, such as a kidnapping.
Keep your IMEI in a safe place. Consider insuring your phone and keeping regular backups of your contact list and other important information on your phone.
Some smartphone manufacturers offer phone tracking apps that can help you find a missing or stolen phone. Check in the app store for your make and model of smartphone.
If your phone is stolen, report it to your service provider immediately, as you will be billed for phone calls made on it.