thats a toll free number you should be able to dial it directly or UK international code + that number
according to definition of toll free, dialed party has to pay http://en.wikipedia.org/wiki/Toll-free_telephone_number so you may not be charged for it even though you use to call without international plan. but better to ask your phone company because if you dont have int plan and called outside (from my experience with normal phone number), they charge you alot more/min. or you can use phone card.
You dial 001, then the rest of the number. Like here in the UK, you probably have a phone code 0...like mine is 019, but you take away the 0 when adding the code, but you don't when calling numbers like that. I think...
Maybe this has been answered above, maybe not. That is a toll free number in the US. I should think if you dial the country code for the US and then that number you should connect. Sorry I don't know the country code for the US.