I've still got 11 months or so left on my 2 year family plan with AT&T, but I'd like to buy an android phone now and sell my existing Samsung Impression. What is the cheapest Android phone that will not switch me to the smart phone data plan? I'm currently on the $15 unlimited dumb phone plan. The G1 looks cheap, but will an unlocked one trigger the plan change with AT&T? Is there anything else I should be looking into?