When I unlock my AT&T iPhone 3gs, can I complete the unlock using the original sim card? I don't have a different one, I will purchase that later when out of the country.

http://support.apple.com/kb/HT5014

Not that I am aware of ,We have been unlocking iPhones in UK for at least 3 years

and frankly the only way there has ever been is to try another sim

Know anyone visiting from outside US and could try their sim ?

Is T-mobile GSM ,if so try one ??

Hello there,

I have a similar question.

Once I've unlocked using a different sim am I then locked into the network of the new sim or can I change sims/networks whenever I like?

Thanks

David

as one of the other repliers indicated (implicitly) - you can complete the unlock using your original sim card - to complete the unlock you have to restore the phone in itunes - if its unlocked you should get a message from itunes that says

Congratulations your iPhone is now unlocked

but the only way you will really know it worked is to use a different sim card

that what i did - i

1) restored the iPhone with the original sim card and got the congratulations message

2) installed a pre-paid sim card from another carrier and made an received a phone call

Used SIMs are super cheap. AFAIK, they don't need to be active in order to unlock. You can probably get a T-Mobile SIM for a couple bucks on eBay.