How to unlock Iphone 4S with no sim card?

I bought an iphone 4s and i want to connect it to tmobile so i restored it to the factory settings, thinking that's all i had to do. But then they told me i had to jailbreak it, thing is its asking me for a sim card (that i don't have) so now what can i do?

If it's an AT&T phone there's absolutely no reason to jailbreak the phone. It voids the warranty and you'll just need to do it all over again on the next update. It's a waste of your time and efforts. You can basically buy a factory unlock now for all generations of AT&T iPhones. Go here: http://gsmunlocklabs.com/unlock-iphone/

you can wrap it up in about 4-12 hours using that service, your new sim and itunes. It's super easy and it's a permanent unlock. You'll never have to worry about it again…