How to check if my 5s is really unlocked?

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I unlocked my ATT iPhone 5 about 2 months ago.

first time, I chose to restore from backup, and I DID NOT get the congratulations, Blah blah blah message. I check if iPhone was unloed by putting a T-Mobile in it and it worked.

A few days ago I was fooling around and I did a reset, and I could not remember the password, so I set it up as a new iPhone, and I DID get the congratulations message in iTunes.

Then I was able to find the password and I was able to restore from the backup. Most my data (sans some Apps) is back as it should be.