My truck has H7 bulbs and you're correct. They all come on at the same time. H7 bulbs have one filament, unlike the H4 that has two. My i10 has dipped beam or high beam on at one time. Never at the same time. I think someone is trying to make money out the OP.It's possible but it's just not the way it works on your particular model, or any other model that is fitted with H4 bulbs AFAIK. If your car had H7 bulbs, like a Santa Fe for example, your dip beam probably would stay on when the high beam is on.