How to totally block internet access (data) on an Android?
I think the best solution you can take is to disable the 3g connection (data traffic) option in Android because its state remains the same as when was turned off. 

There's a thing in Android called shared preferences for each application installed. Settings is also an app and the saves there its actual state, parameters and configurations. So, when the phone turns on again, Android (settings app) reads that preferences and restores. So the 3g will keep disabled