SpareOne is SIM unlocked, so it can accept SIM cards regardless of the GSM operator, and micro-SIM adapters are also available for iPhone users to insert their iOS SIM.

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By default, Apple will sell these at full MSRP in a "SIM-in unlocked fashion, " as confirmed to us by an Apple representative here at T-Mobile's event in New York City.

ENGADGET

Of course, the easiest and cheapest thing to do is convince a friend to loan you their unlocked GSM smartphone and buy a SIM card when you arrive in the UK, and then Dublin.

ENGADGET

If your phone is compatible, you'll need to decide whether you want to get your phone unlocked so that it can accept a local SIM card -- the ID chip that carries your local phone number.

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The 35 Carbon, 50 Platinum and 53 Platinum all cater to the budget, carrier-independent crowd with common foundations of unlocked 7.2Mbps HSPA 3G, dual SIM slots (only one being 3G) and stock Android.

ENGADGET

Assuming that you have an unlocked iPhone 4 or 4S or Android GSM (which is usually unlocked when sold), you can insert a local SIM card and have local voice and data services at a fraction of the cost you would otherwise pay.

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