Never fear help is here! Getting those text message alerts is definitely important. I don't want you to miss any important text messages. Text messaging is my main means of communication so I definitely understand your concern.
My brother had this same issue and we found a solution. You just need to make sure some settings are correct.
Go to Settings>General>Accessibility>Turn assistive touch "ON">Click home button>Tap on the White circle in the top left hand of screen (assistive touch button)>tap device>tap un-mute> Test the resolution> disable assistive touch following the steps listed earlier> then test again.
If this does not help you will need to perform a backup/restore via iTunes http://vz.to/ZIbIge. Keep me posted if you need further assistance.
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