I have just purchased an iPhone 4S. It is running iOS 5.0.1 which is the latest version but there is no Siri and there is no "voice to text" button on the keypad. When I hold down the home button, the old "Voice Control" feature is activated.
Are you certain it's a 4S? Physically, they look nearly identical. It's possible your vendor might have given you the wrong unit. That behavior sounds exactly like the standard iPhone 4 with iOS 5.
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