Unlocking iPhone 3GS for overseas use

Hello everyone,

I have used Redsn0w to unlock and jailbreak many iphone 2G's and 3G's, but I am currently planning to unlock a 3GS. My 2G and 3G iPhones unlocked successfully and worked with AT&T MVNOs and T-Mobile, so I figured everything was fine.

I went overseas (Turkey and Pakistan) and tried using a Ufone and Mobilink (Pakistani carriers) SIMs, but had no luck. The phone just showed one bar and no carrier name, nor did it say "no signal". I want to unlock my 3GS such that it can work with these carriers, as well as Telenor, but I am not sure if there is a separate procedure one must go through. Any advice?

Information on mobile carriers in Pakistan and frequency bands:
http://en.wikipedia.org/wiki/List_of_mobile_network_operators_in_Pakistan

jmunlocks said:

You can factory unlock your iPhone through us, jmunlocks.com

Click to expand...

What option would I select if I want it to work for a carrier in Pakistan? Currently I have a US purchased 3GS


----------

Any way to do it myself, instead of paying for it to be unlocked? What advantages are there to the IMEI based vs software based?

Does anyone know the particular reason why my current method did not work the last time I tried it?