How do I know if my iPhone 4 is unlocked?

Question

So I had lost my original iPhone 3 weeks ago.  And I had to go out to buy a new iPhone without contract for $699. 
The new unlocked iPhone came out this week for $749.  So i decided to go to the apple store and see what they can do since I wanted the unlocked iPhone.
They returned the phone I got .. and they just resold it back to me.  They told me to do a restore from backup and it should be unlocked. 
Now, how do I tell if it is unlocked?  I bought a tMobile micro sim card from ebay so that should be arriving soon.  but is there any other way to determind that my iPhone is unlocked? 

Answer 1

I think you were given very bad information. If you purchased a new iPhone anytime prior to the last couple of days (when the availability of unlocked iPhones in the US was announced), it was almost certainly locked to AT&T and if so, then no amount of restoration or anything else the Apple Store could do would unlock it.
I don't think there's any way they could have sold you an unlocked iPhone unless they had them in stock well in advance of the day Apple made the announcement. You can wait until your T-Mobile SIM arrives and see if it works, if you wish, but if it were me I wouldn't wait since that might put me beyond the time when the Apple Store could officially accept a return, potentially making it harder for you to get the issue resolved. I really think you need to go back to the Apple Store and talk to them, preferably with the store manager involved, and get absolutely confirmation, with agreement that you can return the iPhone if the T-Mobile SIM doesn't work, that the iPhone they sold you is indeed unlocked.
Regards.