Had to explain problem first; now, a little more solution.
You perhaps see the sea you drown in now. See the water to swim in and above it.
As stated, condition yourself as preparation to improve results. The conditioning and preparation help you deal with being unjustly screamed at, as does understanding the situation.... When screamed at, the general sense of calm created by conditioning helps as a better baseline. Understanding the situation helps you adapt to it.
Example: Rude as hell customer has a problem. Sadly, your job means you are the target of their rage.
Behaviorally, obviously remain outwardly calm. Never let them see you sweat (99% of the time). Distill their bullshit complaints down to easy to understand bullet-points. That way you can devote minimal resources to remembering them and the details behind them. This will allow you to do what you have to in order to avoid negative consequences to you.
Mentally, remembering those bullet-points, imagine yourself in a better place (happy place?), where you are not in this bind. Rather you're basically manipulating your own emotional state, which is hard but possible and advantageous. Actually TheBiggerFish wasn't too far off with imagining they're screaming at someone behind you.
Emotionally, distance yourself and realize they are stupid. Whatever their problem is, they have limited language skills. The best way to resolve problems is talking, not screaming. They will receive nothing good from yelling at somebody who can't really prevent or deal with the problem. They are stupidly wasting their energy. It does not reflect upon you; you are not the cause of all the problems they have, though they are stupidly blaming you. It is unfair and unjust. Their emotional immaturity gives them no right to do this, but sadly our society encourages it. It is not you, this is critical to believe, because they are essentially saying it is you. It isn't.
Professionally, keep that bullet-pointed list in mind. Follow whatever procedure you have to. Don't disregard your training and education because some moron is screaming and demanding it. Customers who scream are stupid and don't know how to deal with their problems most of the time. You gain nothing (and they gain nothing) by going down to their level. There are rare exceptions, but those are few and far between (and risky as hell). This will CYA and usually also deal with the problem the best way you are able. It is their problem and doesn't reflect upon you. Keep saying this to yourself, because it is overwhelmingly true 9 times out of 10.
You may correctly say this is difficult and requires mental processing. Yes, I've found it to be worth it. I hope it may be for you as well. Do you see a little more of the picture now? I hope so and that it helps you.
Let's say this happens:Customer: "I want a refund on this item."
Employee: "Ok, do you have a receipt?"
Customer: "No, but I bought it here. They let me return things all the time at your other branch."
Employee: "I'm sorry Miss, but I can't do a return without a receipt It's store policy."
Customer: "You what?! I've been coming here for 11 years and I've never heard that before."
Employee: "I was always trained to require a receipt before a return. Store Policy."
Customer: "The customer is always right and I've been one for 11 years."
Employee: "I understand you're upset about this situation, but without a receipt the company won't allow a return."
Customer: "I want to see your manager." [Lovely snide tone]
Employee: "My manager is out to lunch right now. I'm not sure when she'll be back exac"
Customer: "O typical! I bet you just don't wanna do it!"
Employee: "No Miss. I can't do a return without a receipt and I'm sure my manager will say the same."
Customer: "You can't just do a simple return?"
Employee: "Not without a receipt, no Miss."
Customer: "I want to file a complaint with your boss or the store or whoever."
Employee: "I'm sure if you do they will also say a receipt is required Miss."
At this point, either the customer will devolve into screaming, report to corporate, or give up, but ultimately, you can't control what she does. She's a moron, and rather than try to find some alternative way to resolve the situation (going home and getting a copy of her credit card statement and coming back to politely see the manager with it or something), she's proven she's a jerk. Threatening the employee does nothing good for her, except fulfill her desire to complain and ruin another person's day.
CYA (Cover Your Ass). If possible, you want to document this thing after it is over. Note the time, date, and basics of the conversation. Remember those bullet-points? Customer wanted a return without receipt; I politely and repeatedly informed her store policy didn't allow this. She attempted to blame employees for this. I simply repeatedly restated policy. Tried to give customer the option of waiting for manager to come back from lunch; she cut me off. (or whatever your store policy / manager told you do to / follow your training). She's gonna complain if she's gonna complain, but this way you at least have your story straight.
Mentally, have those bullet-points, "Customer wanted return without receipt; was told store policy doesn't allow.
Manager at lunch; tried to suggest solution; was cut off.
Customer argued and intimidated; I remained polite.Meanwhile, I'm on a marble Terrance in my mind. Three lines to remember. Mental and emotional distance. Repeat bullet-points; insert, "I am solving not causing this." When situation ends, document it quickly, writing down bullet-points, time, date, etc. That's the plan anyhow, and yes it certainly is hard, but I contend worth it.