Unlocking sim after soft update

Hello! I own an iPhone 4, iOS 4.3.3 BB 03.10.01.

I wish to update the soft to 5.1 with preserved baseband. My question is, after that, do I need the sim from the carrier the phone's locked on, to unlock it? The phone is locked on some french carrier, i have no idea what it is and obviously i have no such sim cards. Thank you, would be great if you could answer :)