Can I put a contract sim into an iphone?

I currently have a 24 month samsung chat contract phone with tesco, I know someone who is selling a 1 month old iPhone and I was thinking of buying it. But what I want to know is would I be able to put the sim from my phone into the iPhone and still receive my contract, unfortunately I don't know what network the IPhone is on but I would guess it is orange or O2

Yes it is possible to use your sim card in an iPhone. As long as the iPhone is unlocked to all networks. If it not unlocked then it won't work. Also remember to check it makes and receives calls on the network it is on as it could be barred as on reported list or stolen. Unlocking costs depend on the current network it is on. We in our company unlock iPhones everyday whether it is a special sim or a software unlock.Mr K managing director at Scottish mobile services