Not able to activate new iPhone from India in US.

I bought iPhone 5 from India and immediately traveled to US. I didnt even once connect it in India. I got nano SIM to use in US from my company. When I am trying to use this iPhone 5 in US now with new SIM for first time, it is not getting activated / unlocked. I tried to restore using iTunes, tried using local SIM from US. Nothing is working. Talked to AT&T - they saying talk to Apple. Tried calling Apple - they could not help. Only reason I got iPhone here was to be able to do facetime with family back home. Please help.