O2 in the Uk do pre paid sims with credit that doesn't expire as long as you make or receive a call once every couple of months, they work anywhere in the world and are very cheap, you can normally buy them for £1 on line direct from the website.

I checked out that website above and oh my god!! $40 dollars for a card that are nealry given away

Link to there website where you can find out the charges for calls in a specific country

http://travelabroad.o2-uktech.com/coverage.php?n=b

Dino