I live in the US, and my friend lives in Northern Ireland, and wants me to call him. But every country code I have tried, either calls someone that isnt him, or says "the international call you made cannot go through" or something like that. I dont know if maybe there are more country codes for calling his area, or if there are different area codes I have to dial, because nothing has worked so far. He got his phone in London, so would that have anything to do with it? How do I make a call to Northern Ireland?