Beware, if it's the same type of "adjustable" stem as my Navigator 200, it's basically got a hinge in it (don't know what it's actually called
) so you can only raise the stem by effectively shortening it. So you could try that, but be careful of bringing it too high and winding up with an effectively extremely short stem.
It's quite possible that they put you on a bike that's too large for you. I know my Navigator is too big for me - it's not a huge issue since I never ride it more than about 10 miles at a time. One thing I did is roll the handlebars back a few degrees to bring the grips closer to me without changing the handling too much. Or possibly your LBS could swap you some handlebars with a little more pullback.
I will say that the saddle that came on mine is HORRIBLE. So if you find one that fits better, by all means swap it out.
Speed comes from what you put behind you. - Judi Ketteler