Can I purchase an iPhone 4, without receiving or having to buy a sim card with it?

I currently have a blackberry curve 9320. My contract is with 02. I got my contract in September and it lasts for 2 years. I really want the iPhone 4 or 4s. As I don't want to be paying to contracts, am I able to buy an iPhone lets say from Amazon, or somewhere which is reliable (Please could you note some places) that I can get JUST a phone without a sim card. Also if I'm able to purchase an iPhone with no sim card, will my sim card with 02 (if i get a mini micro chip one, from 02, where they have put my number on) work?

So you basically want a factory unlocked iPhone 4. Those can be bought from Apple but are more expensive than the locked ones.