The front piece is the adjustable objective. Changing it should not change your point of impact. Just like changing your magnification shouldn't change your poi. Your scope is bad. The turrets which are circled in blue and yellow are the only things that should change the poi when turned.

That being said, I've got a couple of friends that love cheap scopes and mostly use Tasco and Simmons. They both had horrible luck with BSA's. I figure if they were unhappy with them after seeing some of the stuff they like, it's no way I'd be happy with one. I'd upgrade to something a little nicer if it was me.