I just purchased a use unlocked and jailbroken iPhone 8GB 1st Gen a few hours ago. I intend to use this unit with my current T-Mobile plan for a few months before switching services. My plan is very basic without data (EDGE), and only a handful of text messages. I want to avoid all unnecessary charges as possible. My question is as long as I turn off EDGE though Bossprefs and use internet through Wifi should I get any extraneous charges? Are there any other precautions I should take? I also know that iPhone uses visual voicemail...is it possible for T-Mobile to charge me for something similar for just checking my voicemail? Is there anything else I'm missing? Any tips would be great...thanks!