find some meaning in these wonderful tidbits. i think you'll find hidden answers in Apples questions and answers.
Can I use the SIM card from my current mobile phone?
You should use the SIM card that came preinstalled in the iPhone.
Can I “unlock” iPhone and use it with another wireless carrier?
AT&T is the exclusive wireless carrier for iPhone in the United States. If you currently use another wireless carrier, you can choose to transfer your number when you activate your AT&T account.