Hi, I'm from Puerto Rico were we currently have At&t with the best reception but is so much more expensive than the competition, hence T-mobile. I found a way to make the jump for a very good plan in T-mobile. I would like to know if an unlocked iPhone 6 from At&t will work for with T-mobile and if the LTE will work. Also since T-mobile already has the WiFi Calling, will this option be available in the unlocked At&t iPhone 6 or not? If I go to Settings -> Phone, now it only have the regular options and one that says "At&t Services". There is no WiFi calling option. Will this be available with the unlock? Any help will be greatly appreciated.