Also on the website it states that the sights are fixed, but in the owners manual it says the rear is adjustable with a brass punch and hammer...
It is fairly common for "fixed" rear pistol sights to be drift-adjustable for windage. Most shooters don't consider such sights to be adjustable per se.
As with the other posters, I suggest getting some instruction and letting someone else test the pistol before attempting to adjust the rear sight. It's most likely shooter error.