Same, I work for a secure psychiatric hospital and often have to deal with distressed family, friends and visitors. I've also worked in debt collections, private investigation, personal security, close protection and airport security. Some of the most hated jobs in the world it seemsThis is pretty much it. I used to work retail and tech support, the behavior of some people.
Nowadays I find that being polite/not an ******* often get me really far.
When I have to ring any customer service or visit retail stores the staff react so surprised when I ask how their day is/was today and how they are. Also remembering someone's name they gave you at the start of the convo (not a common thing in the UK) goes a long way to getting treated the way you want to be treated and the way you should treat others. With respect and mindful of others dignity and human emotions.
Of course we are all human and it's hard to keep a level head when you feel you have been wronged, but there is always a polite way to push your agenda and respectfully pursue your customer rights and consumer law.