Solved: how to hard reset Orange SPV C500: Power off phone. Press both LEFT and RIGHT SOFT keys, then...

Orange SPV C500 hard reset with keys

Power off phone. Press both LEFT and RIGHT SOFT keys, then press POWER for a few sec. Keep holding these 3 buttons until you see

"Press 0 to restore factory default, other keys to Quit."

Press 0 to hard reset Orange SPV C500.