It's also her job to be polite!

That was immature on her part to say "jeez" and show outward frustration on customers.

Well do you have a loyalty card?

She should be polite regardless of what you said/what expression you were making.

People are so quick to judge, anyway isn't it apart of her job to be polite

I know how you feel, OP; strangers have commented on how pissed I look on more than one occasion. I've gotten into the habit of shaving my eyebrows and drawing on less angry ones with Sharpie. Now I walk around with a perpetually sincere yet inquisitive look on my face. Well you're at it, you can also draw eyes on your eyelids in case you want to rest up during a particularly boring conversation without offending anyone.

I would explain to the lady that you didn't hear her and your face naturally looks angry.

I get things like that a lot,it's the resting bitch face syndrome!

Same thing happened to me last week . Feels bad man

I know the feeling OP; I have a naturally unhappy looking face so people always ask me to smile in group photos, but I thought I already was smiling.