Will i be able to unlock iphone 3g baseband on ios 3.1.3 if i update normal mode?

I have an iphone 3g jailbroken but the baseband is 6.15.00 which make it unlocked but every time i try to update from 3.1.3 to 4.2 using a custom firmware, itunes returns an error 3914.so i would like to know if i update in normal mode, will i be able to unlock it? And tell me what will be my new baseband

Please read the DEV-TEAM Blog… They are the prime authority in jailbreaking/unlocking iphones for free. Make sure you read their old posts! Also try "iClarified"

If you update it, you will lose unlock, but you can find some websites to unlock your iphone.
try the website that my friend has used it to unlock his iPhone for permanent.
it seems they are official apple unlockers.their price was about $25 and they did a remote unlock by getting the iPhone imei number. They unlocked my friend's iPhone in just 12 hours.

take a look at their website: http://officialappleunlocker.com/