iPhone 3GS Jailbreak/Unlock Issue - Help Please!

[FixYouriTunes]

Hi everyone. I'm trying to find out if iPhone 3GS with 4.1 operating system is possible to jailbreak?

I thought it was.

I watched a bunch of videos on youtube and did plenty or research online and my research led me to believe that I can jailbreak my iPhone 3GS with this software:

http://www.greenpois0n.com/

I did that and unlocked the jailbroken iPhone within Cydia in and ultrasn0w. It seemed all done but I had an interested buyer and he took out the sim card and added a T-Mobile sim card and he mentioned it was not unlocked.

Any ideas as to what could have happened? The phone indicated that ultrasn0w was installed. Did he not know what he was doing? Just needing to get this resolved so I could move on. Any help would be appreciated.

 

[PsstGreek]

iPhones on 4.1 can only be jailbroken. The new baseband cannot be unlocked as of yet. But in order to unlock, a jailbreak must first happen. Then an unlock can happen by installing ultrasn0w if the baseband is unlockable.

 

[Applejuiced]

Yes, like said above.
Jailbreak yes, unlock no.
The buyer is right, even though you installed ultrasnow the 4.1 baseband cannot be unlocked so it wont accept anything but AT&T sims for now.