can you please tel me something, i want to buy iphone 6+ from some carriers for 300$ in US, but i wannt to send one to my son in europe in serbia, so please answer me this, if buy some iphone6+(gsm or cdma) from at&t or verizon,or tmobile will it work in serbia? i heard some LTE phones are unlocked,in serbia they use regular sim cards, they dont have LTE, i think sim cards are 3G(128k) GSM 900 i 1800MHz so will those iphones from att or verizon work on serbian networks on gsm?