I have a Lumia 520. Did register my phone for dev prieviews as you all know that wo 8.1 is due this week. I want cortana on my phone but they aren't releasing it outside of the US until the next year. My phone is an unlocked Indian variant, so I want to flash the us at&t rom on my phone. Now, the question: the phone is sim unlocked, would flashing the at&t version lock the phone to their carrier. Remember, I live in India.