I got given an iphone by a mate at school as he couldn't get it to work on Orange. I tried my sim in it and it didn't work either. My dad said it was cos the phone was locked and i'd need to phone the network to get it unlocked. The trouble is we didn't know which network to call.
My dad found this site online and sorted everything out with them and it all works now. I am using my pay as you go sim card in it and can download apps, sms, everything. Pretty cool website - fixed my iphone :)