I've decided the phone I want is a Blackberry Curve. I already have a contract that is $40/month with AT and T and suits me perfectly. I don't need anything more, as all I do is talk and text message minimally. I will also want to use internet minimally on WiFI if that is possible. Is the cheapest route to just buy a curve, pay to unlock it, then switch in my current phone's AT and T sim card (can I even do this?)? I definitely do not want to pay the termination fee for AT and T as it is ~$200 and I am satisfied with the service. TIA.