I'll have to check my standover height when I get home.

If your saddle is too low, which I'm thinking it is for you, you end up putting a lot more strain on your knees and you also end up working your quads a lot harder than they have to.

If it's too high, your pelvis will tilt in order to reach the bottom of the pedal cycle, which is no good either.

Is there another shop you could take it to, or even another person at the same shop, to get a second opinion?