ok I've searched and searched and can't find a definitive answer. I want to pre-order a no commitment iphone but don't see any option on Apple or AT&T's website. If I buy one as a new customer, can I cancel within 3 days and pay the difference ($699 - $299 for the 32GB) plus the $325 ETF and keep the phone using with my existing (trimmed) AT&T sim? I'm not sure if AT&T will force me to return the phone else mark its serial number "unusable" in their system rendering it useless. thanks!