Im sorry to hear that the problem is still there.
If it's not software issue, or the SD card, then the problem could be more complicated. Usually for this kinda of issue, the sevice guys will just replace the motherboard or the phone itself. Since pretty much everything else is soldered to the board.
Bring back your phone for service and explain to them what have been done to try to fix it.
They would need to keep the phone for a few days for further testing though.
