Error 1015, tried using Recboot, iReb, fixRecovery

Please Help!

I wanted to sell my iphone 3gs and therefore had to remove all the personal data (sms, emails, contacts). I thought the “Erase All Content and Settings” would be the best option. Once I clicked that the iphone became unresponsive for about 1.5 hrs. I thought it was stuck and so I restarted it, and ever since then I’ve faced a series of unfortunate events. I m just not able to fix it…

The iphone was jailbroken with baseband 6.15.0 and I can’t exactly remember the firmware, but I know it was 4.X.X.

I’ve tried restoring it to both original (directly from itunes) and custom firmware 4.2.1, 4.3 and 4.3.4 (from http://www.felixbruns.de/iPod/firmware/) via iTunes, and I keep getting error 1015.

I’ve tried Recboot, iReb, fixRecovery43 to fix this and nothing seems to work, the phone is stuck at a screen with the usb cable and itunes logo

Please help and let me know whether there’s hope and a way out…
Thanks,