Can I use an unlocked iPhone 4S without data plan for Tmobile?

I currently have a prepaid plan for Tmobile, which already pays $100 for a thousand minutes. I want to use an unlocked iPhone 4S for my Tmobile but I don't want to be charged with data plan and I don't even need the 3G at all. Will turning off cellular data entirely help avoid data fees as well? Anything I can do to use my unlockediPhone 4S without any data?

I recently tried an unlocked 4S on T-Mobile as two reps at the local. Apple store told me the phone would work on any GSM network and specifically would get 3G speeds on T-Mobile's network. Not true---EDGE speeds only despite Tmob having an extensive 3G network in this area. An Apple customer care supervisor confirmed that an unlocked iPhone is not able to use Tmob 3G, confirming my experience. It apparently is a hardware problem - the iPhone chip does not communicate on the freqencies used by Tmob for its 3G network, so there is no work-around.
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