I'm leaving the country on the 10th and need to make sure my AT&T iPhone works until I get back. If I pre-order the Verizon iPhone at 3am tomorrow morning, at what point is my AT&T contract over and my phone dead? Is it after I activate the Verizon iPhone, as soon as I complete the form during my order or at another point? I want to keep my AT&T service active until I get back from vacation. Thanks.