I believe that the iPhone does not save the contacts on the SIM but on the phone's memory instead. It uses iTunes to synch your contacts.
I just sold my iphone, got sick of the fingerprints, attention it got, and also how careful u have to be with it in public. My question is, I now have a blackberry curve 8310, att gave me a new SIM card, I put in my att SIM card, but all my contacts r gone! Is there anyway of finding them on my back up on my computer. Because in Jan. I had my Iphone replaced due to tech problems and it was able to load my contacts in Itunes.....any help would be much appreciated!! I lost over 100 contacts