I'd have to see the fit.. As 'Size' in bikes is the distance from the crank axis upward along the seat tube
to some point at the top of the frame , its that someplace that is not agreed upon..
top tube horizontal or does it slope? what is the slope ? seattube extend a ways above the top of the top tube?
Issue could also Be the BB height is further off the ground. also..
You probably should have not let them talk you into that size in the 1st place ..
just had it a week or so?, go exchange it.