How to Unlock 6.1 iPhone 4 on 04.12.05 Baseband?

I have iPhone 4, it was running iOS 6.0.1, and has just upgraded it to iOS 6.1 few hours ago. But now I have a problem after upgrading my iPhone 4 to iOS 6.1, it give me no service on the signal bar, ultrasn0w is not working now on my iPhone 4 with baseband 4.12.05, so how can I unlock it to use it on any carrier?

Ultrasn0w won't work with any baseband higher than 1.59.00, so that it will not work on your iPhone 4 which running iOS 6.1 with 4.12.05 baseband.

Unlock Methods:

-Sam Unlock <= Not applicable for your iPhone
-Gevey SIM <= Not applicable for your iPhone
-Ultrasn0w <= Not applicable for your iPhone
-IMEI Factory Unlock <= Applicable

As recommended by iPhone Dev-Team, the only solution for your case, is to turn your iPhone to factory unlocked iPhone by using the IMEI unlock method. This method is an official unlock for your iPhone and is also a life time unlock.

What you need to unlock your iPhone using IMEI Factory Unlock?

1- Your iPhone IMEI (by dialling *#06# or on Settings > General > About)
2- You have to know the official carrier which your iPhone is locked to (not the carrier you want to run your iPhone on)
3- Send them to trusted IMEI unlock provider

NOTE: There are many scammers over the internet. Here's a trusted service provider, MyIMEIunlock LTD is a 5-Stars Google ranked and verified factory unlock service provider that can permanently unlock iPhone 4 http://myimeiunlock.com/

I have used this website once and it was great they do other carriers too not just AT&T.
official-iphone-unlock.com

Dear Nada.

Unfortunately there's no way to unlock 04.12.05 baseband at this moment, except factory unlock.

But if you need more information, go here: http://www.letsunlockiphone.com/methods-unlock-04-12-05-baseband-iphone-4-ios-6-1/ and find out why it is impossible to perform and what to do next.

Also you can send me PW with the IMEI # of your iPhone and I'll will help you.