How to unlock iphone 4 with 04.12.05 baseband?

I just got a iphone finally from my older brother. And i would like to unlock the phone so i can use it with my sim card. I jailbroken it using evasion and tried to install ultrasnow but it did not work.
iPhone OS is 6.1.2 and baseband is 04.12.05.

Please let me know my best bet besides having to pay for a unlock website. I'm really trying to achieve this myself.

I will help you.
What's your locked carrier?
You can unlock your iPhone 4 using Remote unlocking method. It's one of the best and safe way to unlock your phone at low cost. For iphone unlocking visit http://www.wickedunlock.com/apple-iphone-4/rs16wp9/ I hope it will be very useful to you.