How to make sure if the iPhone is unlocked?

Hi!

I recently won a giveaway on a certain website of the iPhone 5, but they're located in the UK. I'm not from the UK. It's legitimate, I'm sure. But that's not my problem. My problem is that he's implying that the iPhone's unlocked, but how can I be so sure? Is there something on the packaging that indicated whether the phone inside is locked or unlocked? Help!

Please and thanks!

Instructions

1

Open the SIM card slot located on the top of the iPhone.
2

Remove the SIM card from inside the iPhone.
3

Insert the replacement SIM card and close the iPhone.
4

Turn on the iPhone. Wait up to two minutes, then try to place a call. If the call works, the iPhone is unlocked.

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