YSK that if you interact with a nice worker in the service industry, calling the company they work for to praise the worker will usually provide a tangible benefit to that person's life. Just don't mention discounts or cut corners.
from /r/YouShouldKnow
YSK认为，如果你与服务行业的好工人交往，给他们工作的公司打电话表扬该工人，通常会给这个人的生活带来切实的好处。只是不要提到折扣或偷工减料。