When I was at Staples, the were like "customers say they are scared to approach you because you always look angry"
I told dude that i cant fake smile, I look insane...and I showed him...The dynamic changed to them introducing people to me first so they would know I just look mean, but actually have a high tolerance for bullshit because my emotional barometer is pretty isolated.
Luckily, I only had that job a few months and no one has asked me smile since...