Reinstall iphone HELP!!!!

[usamabineddy]

donno if this is a stupid question but just bought a iphone off a mate cause he got the new nokia n97 and i reset/deleted all setting and data to get rid of all his crap. the phone then came up with a screen allowing emergency calls and one with the itunes icon and usb picture. i downed the new ver of itunes and plugged the phone into the usb and it comes up as "Sim card inserted into this phone does not appear to be supported" i put my old pre paid telstra 3g sim into it. he was on an optus plan when he got it. when i take the sim card out it says "insert a valid sim card with no pin lock to activate iphone" pleaseeeeee help. will buying a prepaid sim from his carrier work aor what do i doooo......

 

[ste1164]

It sounds like the phone is locked to the previous carrier. If you wanted to use your sim you would need to jailbreak and unlock it.