okay so i found a broken iphone 3gs on the streets of our neighborhood while jogging..
i think it fell from someone's pocket and got ran over by a car..
curious about the phone, i got it fixed up and hoping that i could use it..
but when i connected it on my itunes, it automatically upgraded to FW 3.1..
i knew nothing about iphones back then coz it happened a week ago..
now i know a little about the FW, JB and unlocks, and amazed about this phone's capabilities, i want to use it but when i tried to downgrade it back to 3.0 just to jailbreak it and wait for the unlock of the baseband, it crashed and had a 1603 error..

now when i tried restored it back to 3.1 using the update from itunes, it doesn't want to activate..i use the old at&t sim that i found the phone with..its deactivated..
now its stuck on the "slide for emergency" thing with icons of a USB connector and itunes..
the whole restoration went smoothly but when the phone is being activated by apple, it says that i need a valid simcard..
i really want to use this phone and i don't want the 150 dollars (the digitizer was smashed..i had to take it to a repair center..) that i've invested on repairing it go to waste..
can someone tell me what to do?
i'm a newbie on iphones but i really want to use it on a t-mobile..
please help me..