When I went to the dentist the other day, the staff member who took care of me was really unpleasant.
I had to deal with a really unfriendly store clerk at the lady's clothing store I went to yesterday.
この場合、次のように言うと良いと思います。
ーWhen I went to the dentist the other day, the staff member who took care of me was really unpleasant.
「この前歯医者に行った時、担当してくれたスタッフがとても不愉快だった」
unpleasant で「不愉快な・嫌な」
ーI had to deal with a really unfriendly store clerk at the lady's clothing store I went to yesterday.
「昨日行った服屋で、すごく愛想の悪い店員に当たった」
unfriendly で「愛想の悪い・不親切な」
ご参考まで！
カナダ 
