i guess The IMEI (International Mobile Equipment Identity) is a unique 17 or 15 digit code used to identify an individual mobile station to a GSM or UMTS network. The IMEI number provides an important function; it uniquely identifies a specific mobile phone being used on a mobile network. The IMEI is a useful tool to prevent a stolen handset from accessing a network and being used to place calls. Mobile phone owners who have their phones stolen can contact their mobile network provider and ask them disable a phone using its IMEI number. With an IMEI number, the phone can be blocked from the network quickly and easily.
It is important to note that swapping a SIM card will not stop a phone from being banned. IMEI numbers are stored in the phones themselves, not on the SIM cards.
An IMEI is only used to identify the device and does not relate to a specific individual or organization. Other numbers such as the ESN (Electronic Serial Numbers) and MEID (Mobile Equipment Identifiers) can link an individual to a phone. Usually, an IMSI number stored on a SIM card can identify the subscriber on a network.
And i hope this helps.