If you want to unlock your iPhone to use it with another carrier, it will be necessary to know its IMEI. See two very easy way to know it.
- Go to Settings on your iPhone.
- Click on General.
- Click on About.
- Scroll down. You will see IMEI number.
- iPhone Phone app
- Open Phone application.
- Go to Keypad.
- Dial *#06#
- Then, a window is open showing the IMEI number.