Arent u able to get into download mode? Seems like you havent flash another s 3 rom so you should be able to get into download mode.
I had dome several stupid thing on phone and thought it bricked but I was able to get working.
Sent from my SGH-T999 using xda premium
Yes, I didn't flash any roms, at least any wrong ones, I've only downloaded the miui for tmobile version but phone turned off when I tried to reboot into recovery, I've tried to boot into download by taking out battery and pressing volume down+home+power and plugging battery but nothing happens..