You'll need your iPhone's IMEI number if you want to unlock it and use it on a different cellular provider.

Turn on Find My from Apple Account settings, and enable Location Services from Privacy & Security This article explains how to set up Find My (or its predecessor Find ...

To unlock your iPhone from its carrier, you'll likely need to contact your carrier directly to cancel your contract.

Find: Visit iCloud.com/find > log in with Apple Account > All Devices > choose missing device. Note: Turn on Location Services under Settings > Privacy & Security to ...