How to Unlock a Cell by the IMEI Number
An IMEI, or international mobile equipment identification, number is a serial code that your service provider uses to identify your phone. If you wish to switch to a different company, you will need your IMEI to purchase an unlock code. This will allow you to remove the restrictions on your phone and switch to any service provider of your choice.
Open the back of your phone and take out the battery. Record the IMEI from the sticker. If it has been rubbed off, dial "*#06#." The 15-digit IMEI will appear.
Find a site that sells unlock codes for your phone model. Expect to pay a fee of between $14.99 and $29.99, as of 2010.
Type in the IMEI number into the search box of the site. Select the manufacturer of your phone in the drop-down menu. Find the model, the country where your phone is registered and the service provider. Put in your payment information and an email address. The site will send you the code in a day or two.
Turn your cell phone off and remove the battery and SIM card. This is the white rectangular card underneath the battery.
Replace your SIM card with one from another cell phone service provider. You can either borrow one from a friend or purchase one. Replace the battery and turn on your cell phone.
Enter the unlock code that you received in your email when the phone requests it. Click "OK" and wait for your phone to restart. You will see the new service provider's name at the top of the screen.