UK iPhone carrier O2, Apple's iPhone partner, has teamed up with micro-blogging service Twitter to turn Twitter updates into free text messages for @ replies and direct messages.

From the start of August, every O2 customer will be able to switch on text notifications within Twitter and receive replies and direct messages for free. They will also be able to send updates to Twitter as part of their normal text message bundle or for the cost of a normal text.

O2 already has similar partnerships with social-networks Facebook and Bebo. O2 is the exclsuive carrier for the Apple iPhone.

Once switched on, replies and direct messages will start to come through by text throughout the day, although users can choose to turn them off at certain times if they so wish.

O2's fair use policy for Twitter texts places a limit of 600 messages per month.

Users can switch on the service in their Twitter settings from 1 August.

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