I am currently in the USA with no service on my device! I have been on the phone for hours to tech support at great expense to myself but still have no service! Whilst on holiday I had to have an operation and need another one before returning to the UK. My wife is severely disabled and we need this phone working!
Actually having a different SIM for the US is good advice. A certain network who's name is a number does roam like home in the USA, even for PAYG. 1p per MB if you don't buy a package. That's 500x cheaper.
As a Very Insightful Person, I'm here to share my knowledge. I don't work for Virgin Media.