Originally Posted by Michael A Cruz

ok. im pretty much just as lost as he is. here's my situation.. i got a new iphone 3gs and it was made in the 46th week of 2011. it is running on 5.1 and is on a tethered jailbreak. the modem firmware is 06.15.00. from what im hearing, i cant unlock this phone. but since its on 06.15.00 is it possible? any help will be appreciated.

Greetings Michael. You can downgrade your baseband to one that is unlockable, unlock your phone and then update to newer ios version without changing the baseband. You can read the guide at this link. I haven't tried it yet myself, as I am waiting for my internet connection at home to get activated. I have a 3GS with 05.16.05 baseband and I will update to 06.15.00 and then downgrade to 5.13.04 (unlockable).

I hope I helped

Edit: Here you can find information as well

Serial No: 859429xxxxx (42nd week of 2009, i assume)
iOS: 5.0.1
Modem Firmware: 05.15.05
Model: MC131C
New Bootrom

Is it safe to flash iPad Baseband to unlock it?