O2 plans to limit the new iPhone 3G to just one device per person when it goes on sale on 11 July.

The mobile operator, Apple's exclusive iPhone partner for the UK, started sending out text messages to customers yesterday to encourage them to sign up for the second-generation handset, which was announced by Steve Jobs at last month's Worldwide Developers Conference.

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In the text, O2 said it expects demand for the iPhone 3G to be very high, adding that orders would be processed "on a first-come, first-served basis so that we can be fair to all our customers", before adding "orders will be limited to one iPhone 3G per customer".

O2 also said it would be writing to customers again before 11 July with further details on how to receive an iPhone upgrade.

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