On the extreme, you can re-ROM the phone so it doesn't have the bloated apps starting out. CyanogenMod is one example of doing it "right". Commercially, a "Google Play Experience" ROM is the best one can get for being bloatware free.
Another nice feature on newer phones (think Android 4.1 and newer) is the ability for the phone to warn, then stop using cellular data when you get to a certain quota. That way, it might stop Internet use until you manually disable that, but it helps ensure you don't go over and get additional charges.