Your dealer might be right in that there's not an issue, or they might not. Hard to tell without seeing the actual unit.
From what you described, it sounds like there's a few possibilities:
1) Blockage in the ducts
2) Blower doesn't blow hard enough
3) External loss from ducts to outside
There's potentially more, but that's some of the first things I'd check.
There's no use crying over spilled milk, unless it's on your keyboard.