how i make voice controlled text iPhone 3G

I have an iPhone 4 (I think).  It is a model MC319LL operating software version 5.1.1.  Is it possible to send a text using voice control on this version of the iPhone?  Does this require an app from an outside vendo?  If so, what are the better apps for this purpose for someone with a deep voice?  Voice recognition doesn't seem to work well for me no matter how well I enunciate.  I'm guessing my deep voice is the downfall.    I say "customer service please" and voice recognition just hears "grooowl."

To those with the obvious answer...I'm not yet ready to move on to an iPhone 4S.  I'm hoping to hold out for the next model release before I upgrade.