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Ajusshi and Ahjuma !!

Saying '아줌마' (ah-jum-ma), '아주머니' (ah-joo-muh-ni), '아저씨' (ah-juh-si) would be considered offensive if said to an aunt or uncle. A lot of Korean people use such words to address restaurant workers or salespersons casually. But we usually say '저기..' (juh-gi) to address them to be more polite. A word for aunt would be - '이모' (ee-mo) or '고모' (go-mo).

You can't call them 아저씨, 아줌마!!

Call them 삼촌, 이모
Uncle = 삼촌 aunt = 이모, 고모, 숙모

In Korea, there are 3 way to call aunt.
이모 = When you call mother's sister
숙모 = When you call uncle's wife
고모 = When you call father's sister

But I think you don't have to memorize these.
Just keep '이모'.