Invalid Sim Card Problem

Right, I have a contract with orange UK and I have tried to put another orange UK sim card in the phone and it just says "invalid sim card"

I done this because I bought a unlock code online and it wouldn't work with another sim in the phone so I tried unlocking it will an orange sim card.

(The blackberry is locked to orange)

Any ideas why this could be?

The same thing happened to me. Then I put in the unlock code and the phone still didn't work. Then I took it to a phone store then they opened it up and finally came to the conclusion that the motherboard was corrupt. But then I got a replacement from my carrier. Sorry to tell you but your phone is gone.