I'm a Canadian living in the US temporarily, and will be pre-ordering the iPhone 7 next week. I know that the SIM-free versions may not be available on day one. My question is, are the carrier versions of iPhones bought from Apple (at full price) unlocked out of the box? A side question is, if I'm on Fido/Rogers in Canada, which US carrier version should I buy here? I'm assuming AT&T since that's who I'm roaming with right now. Thanks.