I have an ATT IP5 S that was unlocked by ATT or so they say. One of the recommended unlock checks is to borrow an sim card from another carrier's phone and put it in the phone to see if it recognizes the different network. I did that last night and the phone said "No Service" or something like that. I think I read somewhere that Verizon phones don't use sim cards and the card that is in their phones is a dummy. IF a Verizon phone is unlocked, later on it can be used with a different carrier. I should note that the sim from the Verizon phone that I used came from a locked phone. Do I need a sim card from another carrier OTHER than Verizon to make this unlock check?