can you put a sim card into an iphone?

[fuji]

i want to get an iphone but i heard u have to be on some sort of plan to get one. im with optus and ive been on my plan for years and years and i dont want to give it up so it is possible to take my sim card out of my normal phone and just put it in?
i heard its locked and u need to do something to unlock it?
can i go to JB HI FI and just buy one or what?
thanks

im confused

[geeth]

Ya sure you can use optus sim in the iphone only if it is unlocked one else if the iphone is locked to some other network provider then it wont accept optus sim until you unlock it ..You can easily unlock the iphone through online providers like SimpleUnlocking.com here they are rendering remote unlocking service to unlock all model iphone from network provider .You must first check that whether the service is available for your country and network provider ..If yes then pay for it and unlock the iphone then freely use it with any GSM sim ...