Yes you can restore an unactivated iphone using the itunes.
Following are the setup.
You are having an iPhone 3g,
you can restore your phone.
If your phone is in the "connect to iTunes" screen then it likely isn`t actually in DFU mode.
DFU mode has to be entered by a user.
The first thing you need to do is download the appropriate firmware
for your device and then try to activate it.
It might work else wait for your activation to happen and then go for it.
Hope this information helps you,
else you can find from the customercare.
I hope this help you a lot.