I had recently used roamsimple for my trip to Western Europe and
Asia.  They offered by far what I found to be the most convinient and
affordable international roaming solutions.  I am Rogers Wireless
customer in Canada and I found Rogers to charge an obscene per minute
rate charge for international roaming. They have a T-Mobile UK based
World card that works in 200 countries at a fixed flat rate. It was
perfect to have 1 number that works seamlessly globally and the best
part of this service was that I didn't have to prepay for anyminutes.
All my call charges were directly posted to my credit card which was
so convinient.