ymon It's actually hashgacha that you're asking about this phone now, because it's a pretty rare (and old) model that I've never seen before. Just today, somebody gave me his phone, and it's that model!
Anyway, I just tried the volume button combos, and nothing worked.
I tried running adb reboot recovery, and it just rebooted normally.
My only guess would be that on some phones, if you put in the wrong code enough times, it'll factory reset.
If that doesn't work, you could try bringing in to AT&T.
Hatzlacha Raba!
