I'm in a unique position trying to unlock my 1st gen iPhone (help please)

[stateofmind]

I have an iPhone with no sim and I have my tmobile sim from my brothers phone and my current att (for the 3g iphone) sim at hand. When I put the tmobile sim in it is not compatible with itunes and when I put the ATT one it says I need to activate the phone. I dont want to activate it because I do not plan on keeping it.

How would I bypass the activate screen and get to where I can actually unlock the phone?

Thanks in advance

[rotobadger]

I could be mistaken but I believe you can just jailbreak as you normally would. Hook the phone up and run QuickPwn. There should be no need to activate first.

[NeoMayhem]

PwnageTool will preactivate your firmware.