Does this number he's calling from cost ME money?

alrighty, so I've finally gotten to talk to my boyfriend thats in afghanistan, and he got a cell phone or something over there...and his number has a + sign then a bunch of numbers after it...maybe 12. So i'm guessing that it's international. i never call him, he just calls me, so does that charge anything to my phone bill, if he's the one that calls me? he said the way it was explained to him was that it only costs him...please help me! i dont want a 500 dollar phone bill!!