How to check if my 5s is really unlocked?

[space-time]

graylocks wrote:
[quote=space-time]
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.

was the sim in when you did all this?
yes. The ATT SIM.