How can I check if my mobile phone is unlocked (i.e. not carrier locked)?

For iPhones (iOS 14 or later):

• Open “Settings” and scroll down and tap on “General” then select “About”
• Scroll down to “Carrier Lock” if you see “No SIM Restrictions” then your iPhone is unlocked

For Android phones*:

• Open "Settings"
• Go to "Connections" > "Mobile networks" and tap "Network operators" (or network providers)
• Temporarily disable the "auto-selection" and manually scan for available networks:
  The labels might vary slightly between different Android phone brands. If the networks list shows more than one network, then it's likely that your phone is unlocked. But if only your primary carrier's network shows up, then you can assume the phone is carrier-locked.

*For Android phones the most reliable way to test the carrier lock is to swap SIM cards or eSIMs and try.