Can i use my Iphone in america?

I'm going on holiday to america on sunday and i want to know if i can use my phone whilst i'm over there. I recently went to portugal and my phone was completely useless, it said no service the whole time. This time i'm going to to call my orange and get them to change it but can i still use imessage without any extra cost to my phone bill.

You did not specify so I have to assume that your service provider is Orange. You can buy a new SIM card in US whose network is compatible (i.e. GSM) with Orange and most importantly your Iphone is unlocked.

Probably not. Unless of course your carrier has some type of agreement with a United States carrier.

imessage works off Wi-Fi; you don't need to worry about that.