Will my iPhone 4S work this way?

I live in the US and me and my family are going on a trip to Nepal. Since my phone has unlimited data, I can do anything anywhere on my phone. The pnly question I have is that will this all work as the same in Nepal? Will I still be able to text, facetime, call people, and use the internet. Please help me. Thank its a iPhone 4S from made from california.

If you have the international plan (or whatever it's called). I believe you have to pay 8-10 dollars extra a month.

My guess is you will have to go to a Nepal vendor and buy a new sim that is specific to Nepal system. In a nation that is purposefully 30 min off the time in the rest of the world, I suspect other things are purposefully unique there, too.