Att iphone 3gs factory unlock code want to use w tmobile service

No, it can not be jailbroken because:
1. It's not an iPhone or iDevice. The iDevice are the only one to get jailbroken because those are consider "slave device", by using a jailbreak you "free" the phone. Same thing with PS3.
What you is an unlock network code. If there is no unlock utilities for your phone brand, then you can contact either AT&T or T-Mobile to get an unlock code free, or pay a website to get an unlock code.

visit this link

Yes, You need to unlock your AT&T iPhone 3GS to use with T-Mobile. You can unlock your iPhone 3GS safer and easier through remote unlocking method. You can get the remote unlocking for an iPhone 3GS from www.unlocking4u.com/apple-iphone-3gs/rs6wp9/ at affordable cost. This site is a legit source to rely on accurate unlocking solutions.
Here are the steps for unlocking an iPhone 3GS through remote unlocking method,
1. Wait for us to send you an email saying your phone has been activated or remotely unlocked.
2. Install the latest version of iTunes.
3. Make sure your Apple iPhone 3GS phone software is updated to the latest version using the iTunes software.
4. Connect your Apple iPhone 3GS to iTunes with a NOT ACCEPTED SIM card.
5. Wait until iTunes detects your Apple iPhone 3GS.
6. Disconnect your Apple iPhone 3GS and reconnect it after 10 seconds.
7. Your Apple iPhone 3GS is now unlocked.

If you need to use a T-mobile SIM into an AT&T locked iPhone, you need to unlock the mobile. You can unlock an iPhone safer and easier through remote unlocking method. You can get the remote unlocking for an iPhone 3GS from www.unlocking4u.com/apple-iphone-3gs/rs6wp9/ at affordable cost with easy unlocking instructions.

Hi,
You can do factory unlock to your Apple iPhone 3gs through Remote unlocking in the site Unlocking4u.com.They are cheap and reliable.I unlocked my mobile using this site So I recommend you to view this site.It will be very helpful to you...

to use any phone on another network you need an unlock code that only your provider can give you. more than likely your provider will not give you the unlock code since it is an iphone, and that is for an iphone with any version. this is because apple and att are in a contract with eachother and it is designed for atts network and wont work properly on another network. also by using it on another network it can cause the iphone to be suceptible to different viruses and it can crash.

You should try using this Download
http://www.youtube.com/watch?v=c3YD1tpAFTg
I haven't Tried this but it sounds like it works

If the iPhone is still under warranty you should take it back to Apple. BUT before you do that you should try and restore it back to factory settings. ie. not jailbroken.
If Apple find out that you have jailbroken the iPhone they won't touch it even if it still under warranty!

Try and restore it with iTunes. Try this first

http://jacko0.wordpress.com/2009/12/19/how-to-reset-an-unresponsive-iphone-and-get-it-working-again/

with putting unlock code in, mostaly provider wil give you unlocking code after one year for free by giving from your imei number , you wil get imei with pressing *#06# or under battery compartment it displayd

What are you doing with a phone without a connection? A SIM is a must for the phone to boot and function. Even a dead SIM would do. But SIM has to be in it. So contact the service provider and get a connection (and SIM). Unlocking may not be required as it is a Quad and 3G phone with all the frequencies.