A question to the iphone experts...
 

I have an iphone that I use outside the US ( no AT&T contract, just a local provider).
If I come to the US for a short visit, is it possible to buy a prepaid sd card from any telephone company so I can use the phone in the US without signing any contracts?
Many thanks for any response!

It depends on whether your phone is locked to your current provider. Try a friend's SIM card who is with another provider and see if it works.

Also, are you looking for voice service only, or for data as well? You can get a prepaid voice SIM from T-mobile or AT&T (lots of other threads), but I am not sure that there is a good (reasonable price and data volume) prepaid data service option.

Yes, I´m mostly interested in voice service but other data service would be handy if it´s not so expensive...
Any other ideas?

I think all phones outside the USA are sold unlocked, no?

No. Just some countries. Belgium & Hong Kong are 2 examples.

The UK phones are generally locked.

Cheers,
Rick

I don't think t-mobile in germany locks them, and in france it is the law to unlock upon request after a brief period. Law in Italy to unlock after purchase if requested. Singapore shows unlocked. Hmm, I guess they are sold in 20+ countries now? I wonder if there is a list somewhere.

Actually, my phone is unlocked so I can use it with the local provider.
If this is the case, can I use it in the US with a prepaid sim card?

yes you can. but if you go with tmobile, make sure you turn 3g off, because the 3g frequency tmobile uses in the states is not supported by the iphone. If you go with ATT there shouldnt be any issues.

AT&T GoPhone
 

I use an AT&T GoPhone SIM when I'm in the US with no problems. They've got a few different options for voice, and you can use PAYG data at $0.01/KB, or add 100MB of data for $19.95.

Here's a link to the AT&T plans

Adrian