An International Mobile Equipment Identity (IMEI) number is a 15-digit code for each individual handset. The IMEI number doesn't have any relation to your network carrier as it is a number assigned to your handset. This number is useful for tracking a stolen or lost mobile phone.
Register with a website like Track IMEI, Mobile Phones Tracker or Theft Record. You simply have to visit the website and submit your handset's IMEI number. If the company's dealers ever come across a cell phone with your IMEI number, they will trace it and contact you.
Call the customer care department of your carrier like AT&T, T-Mobile, Verizon or Sprint, and explain the situation to them. You will have to provide them with the phone's IMEI number so they can trace it. If the thief switches on your cell phone with a subscriber identity module (SIM) card, the phone will start searching for a network. As a result, it will send the SIM and cell phone information to the closest cell phone towers, and the service provider will receive information about the cell phone location.
Contact the police and report the theft. Provide details of your cell phone model along with its IMEI number.
Even if the network provider and police cannot track down the phone's location, you can tell your carrier to lock your cell phone. Your carrier will then blacklist your phone's IMEI number, which will prevent it from connecting to any network regardless of the service provider.
Tracing your cell phone through its IMEI number is not a foolproof method. An adept thief can easily change the IMEI number of a handset using special equipment and software.