Activating unlocked iPhone 4s with SIM but without contract?
If you use the T-Mobile SIM it will only activate the device, it will not create a contract.  If you feel safe you can get it without a SIM, head over to the closest Apple Store and ask them to activate the phones using AT&amp;T dummy cards.

Once you activate the phones, I suggest putting the phones in airplane mode and turn on Wifi, otherwise the phone will constantly be searching for signal which will cause the battery to drain.

Good luck.