Need help jailbreaking/unlocking iphone 3g

[JoEw]

So my mom has been using my old iphone 3g on the old 3.xx firmware i jailbroke and unlocked it for her. But then it was not booting up so she restored it and she landed on 4.2.1 firmware now I need help jailbreaking it and unlocking it so she can use it on T-Mobile again this is what tiny umbrella gave me.

Baseband: 05.15.04-5.8_M3S2

if anyone can help I would appreciate it a lot.

 

[rgarjr]

That BB can't be unlocked with Ultrasnow. Your only choice is to use the iPads BB.

 

[JoEw]

That BB can't be unlocked with Ultrasnow. Your only choice is to use the iPads BB.

please explain what that means i havn't unlocked in a LONG time.

is it possible to down grade to an older firmware?