I Hate It When Guys Dont Take A Hint That Im Not Interested

I went to a 24/7 mart and met a guy working as the cashier. He try to talk to me. I didn't really reply him but because of respect, I answer him formally. When he ask my age before guessing it, I look into his face, trying to tell him DO NOT!
I saw he slightly startled and shivered after that. But yeah, this slightly red eyes guy didn't stop. He keep talking "hey do you need the plastic bag?"..... "I think you need it"

Sigh... I just walk away.