How do you turn 'Text Preview' off on the iPhone 4s?

Hey, i've just got the iPhone 4s (16gb on 3 network, don't know if it makes a difference) but I can't work out how to turn the text preview off, It isn't the same as 3gs or the 4, I've googled it and found someone saying it was in the 'Passcode Lock' Section, but on my phone it isn't. Its not in the 'Message' section either.

If anyone could help i'd be very grateful. Thanks!