I have an iPhone -4G can I use it directly with just change of sim in USA?

I'm planning to go US for my further studies so I need to know whteher I can use my old I phone der in US. I bought from India. So do I have to unlock it? Or I can just use directly and use by taking new sim from US?

It must be unlocked. See this link for further info

It depends on what carrier you purchased the phone from in India. You will have to call them to request an unlock. They will give you more directions from there, but most likely you will NOT be able to use it by just changing the sim.

Here is some info on how it's done with US carriers:

  • Will an iphone 4 change carrier if i just insert a new sim? My brother has inherited our dads old iPhone 4, and it was on O2. But now he has a 3 sim, and he is trying to install it. He took out the old sim and inserted the new one while it was on. And nothings happening. Is this normal? Has he broken it? Please reply as soon as possible!
  • What sim to use in USA and what travel money card to take? Anyone know: 1. A cheap mobile sun card that would fit in iPhone 4 that an Aussie could use in the states for a few weeks? 2. Best/ cheapest money/ travellers card to take?
  • If I just buy an AT&T iPhone 5 can I just put my sim card in it and it'll work? I wanted to buy a new iPhone, and didn't want to have to get a new contract. I wanted to know if I just bought a new iPhone off the internet with my company would I be able to do this, because I'm really getting sick of this iPhone 4. Someone please help me with this question.
  • I want to buy iphone 5 from usa.what should be the price in usa? I want to know that what is the price of iphone 4s or 5 in usa with service provider. I live india & my uncle lives in usa. If he will buy iphone then what will be the cost with service provider would cost them. They are coming in india in 1-2 months if they iphone with service provider then it can be used in india. There's any way that the iphone works on india. I know that may be unlocking can do this. Just please need advice.