Because the iPhone is locked to AT&T's wireless network, Apple and AT&T must answer a class-action lawsuit seeking $1.2bn in damages. The class-action suit also notes that Apple will not allow unauthorised applications on the iPhone.

Filed on behalf of Paul Holman in the State of Washington and Lucy Rivello in California, the lawsuit explains that in the US the SIM chip is locked to the wireless carrier, not the hardware device.

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When Apple released the iPhone it tied the device to AT&T. Switching the SIM with one from another carrier simply caused an error when the phone was rebooted. However, the cellular community quickly tackled the iPhone and found several ways to unlock the phone, allowing users to activate it using another carrier.

On 24 September Apple warned customers that unlocking the phone could render it inoperable when future software updates were applied. Three days later, an iPhone update was released that effectively bricked unlocked iPhones.

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"Apple expressly designed its software release 1.1.1 to disable third-party apps and to disable any unlocked SIM cards, and to create technical barriers to install new third-party apps or to unlock the SIM cards," the lawsuit reads.

The lawsuit also contends that Apple didn't discover that unlocking applications would harm the iPhone as it stated on 24 September. Rather, the suit says that Apple engineered the software update to disable the phones on purpose.

"Version 1.1.1 was an upgrade with limited specific changes and improvements," the lawsuit reads.

According to the lawsuit Paul Holman purchased two iPhones and used third-party applications, as well as traveling abroad. Lucy Rivello said she wants to be able to use third-party apps and unlock her phone to switch to T-Mobile.