Can i change my current blackberry contract to an iphone4 (micro sim)?

Basically i'm on contract for a blackberry 9800 but i really want an iphone, my current cntract doesn't finish for another 7 months so what i'm wanting to know is would i be able to use my current contract simcard in an iphone? The issue that is confusing me is that the iphone takes a smaller sim card so is there any way of switching this? I know i can change my blackberry data to normal data but non of this will be any good if i can't switch to a smaller simcard.

IPhone doesn't take SIM cards.

You can because I've heard a million people say iPhones ROCK!

P.S.:iPhones don't take SIM cards so don't worry too much.