Did i or didn't i unlock my iphone 4?

I had a question i followed these steps to unlock my phone http://www.ijailbreak.com/how-to/unlock-iphone-4-3gs-ios-5-1-1-ultrasn0w-1-2-7/ i did everything step by step. How can i find out if its unlocked? So i can use any carrier

Insert a different card, if it works, then it is unlocked.

Try this one http://www.jailbreak4dummies.com may be it will be helpful for you.