Can I use an iPhone locked by AT&T overseas?

How do I unlock it if it does not work overseas? Its an iPhone 5S.

You can call them and have them do it while you're out of town (AT&T) or jailbreak phone and follow steps.

I would call and get an international plan added to your cell service for the duration of your trip. I frequently travel to france and italy and the calling minutes are around $1.20 and texts are like 5 cents to receive 50 to send. Data is like $50 for every 50 or 100 megabytes.

Don't think this is not a deal! I forgot one time and paid like $7-$10 a minute depending on where i was, and it was like $100 for every 10 megabytes of data i used.

Hi, you can use it as far as you would be using it with their SIM card. If you are planning to plug in another SIM card, then you would need to factory unlock it. That would cost around $60, depending on the contract.

It won't work overseas if you don't get it unlocked. The phone must be factory unlocked for using on other carriers. If you need to get your phone factory unlocked, mail me for references.