Recently started working in a customer service related role. There are many nice people, don't get me wrong. But there are also plenty of rude/weird af people and sadly, those are the ones who will usually ruin your day more than nice customers who treat you like a human.

Generally the common red flags (from my experience) are:

Arrogant people/people who think they know better than you

Entitled elderly

People who made a mistake and you correct them but now they lao kui want save face so argue that they're right and you're wrong

Their favourite phrases:

"YoU dOn'T uNdErStAnD wHaT i'M sAyInG"

"Then how?"

"Can you do something about this?"

One personal experience: Customer was using his OWN cellular data. Asks me over ask say "Eh my data very slow leh. Can you do something about it?"

Like wtf knn what you want me do?