A lot of vehicles have a beam dip adjuster in the cab. Mine pops out when I press the center of the light control selector.

Officially, they are to correct for a heavy load in the back. Unofficially, if you tweak them, you can flip between longer range, and polite as required.

If you watch your lights, there should be a fairly sharp cut-off at the top of their coverage. If that line ever hits a window or mirror, it will look like you are flashing them. If it's too high, either fix it yourself (generally quite easy) or get it fixed.