Presumably folks do want to be able to get data connections at times, just not be arbitrarily changed for apps using data connections when you don't want them to. Due to that having the carrier completely disable data connections is not ideal.
There are a set of changes to disable data connections, as I had provided an OEM package to do so in the older Apache kitchens. Unfortunately I can't remember the exact procedure now.
In any case you may also want to check out
NoData, which is a small program to enable the easy disabling/enabling of data connections.