Cell Phone, IPhone

Taking your second question first, if you use the iPhone only over wifi, there is no charge from AT&T. The only charge would be if you had to pay for the wifi (to get a logon password, for example). You have to be sure that you do not accidentally roam over a cell phone network, though. That costs a fortune for U.S. cell phone customers when they are overseas. Be sure you have disabled all data connection if you take this phone. As to your first question, yes, you can buy a SIM card in London that you can use on your trip. You will have to pay for usage, though, but it is not crazy expensive as it would be with AT&T or a travel phone firm, such as Mobal. Check out this earlier post: For overseas DATA use, local prepaid is best solution

Let me add another point: To use a local SIM card, your iPhone has to permit it. I don't use an iPhone, so someone else will likely answer this. For most U.S. phones, you have to have the phone unlocked. iPhones may require another step.

Sowmya, Could you clarify one point. Are you planning to take a "normal" Cell phone as well as an iPhone on the trip? Whether you take your iPhone or another model, the phone will have to be unlocked in order to use a SIM card other than AT&T. If you're only planning to make a few voice calls or texts, you can roam with your AT&T plan. I believe they offer "Travel Packs" which will reduce your roaming costs somewhat. With regard to data use, it's extremely important to disable the data roaming on your iPhone in order to avoid astronomical roaming charges. One user recently roamed with her iPhone and found a $37,000 bill in her mailbox when she returned home! You could also have a look at www.iphonetrip.com, as they offer data plans. They're expensive though. For basic voice and text, have a look at the websites for Roam Simple, Cellular Abroad, Call In Europe, Telestial or Mobal. They offer "travel SIM's" which are usually based on a UK phone number. They provide consistent rates throughout most of western Europe. The link that Paul provided has good information on purchase of data SIM's using UK Cell networks. I've found that some Hotels provide Wi-Fi with the cost of the room (sometimes a Password required), and other times there's a small daily fee for use. The Hotel websites usually indicate whether they offer Wi-Fi. Ironically, the budget Hotels often provide free Wi-Fi, while the high priced places charge for it. Good luck!

Yes you can use your iphone via wi-fi (in airplane mode) free of charge as long as the wi-fi is free. And yes you must have an unlocked iphone to use a SIM other than AT&T. I have a Mobal SIM that works well, more expensive than a local SIM but I only pay when I use it. Basically we used via wi-fi & used Skype. Save SIM for non wi-fi areas.

Sowmya, go to AT&T' website, and read ALL of their info about the cost that will be incurrecd when you take your IPHone to the EU, and all of the various options that you have. Call them if you have questions. I have taken mine to Europe the last two years. I chose to completly turn off data. Others buy an overseas data package, and closely watch their usage. I sign up for their "World Traveler" call package; it generally reduces your call charges from $1.99/minute to 99/minute. I also signed up for "Global Messenger" which gives you a certain amount of super cheap overseas texts. Be aware that any calls or messages made to your phone, or voice mail, will be charged at whatever rate you have set up. So anyone leaving a message on your phone is adding to your overseas bill, even if they are calling from Redmond. The only way you can get around this is to transfer your phone to Google mail, or some other service. Wi-fi is free, so I downloaded Skype for free phone calls to anywhere, and I surf the net, or send/answer Emails when I am near a wi-fi hot spot.