I would ask them to calm down quietly and tell them if they keep yelling I would call security to come help me

Just listen them untill they come bit cool... If u intarupt them then they will start more. So just be also cool front of customer, if customer will see the patient in you then they will come down. And once they will come down then maximum try to solve their matter. If you still feel difficult then just take support from your seniors or your management. 😊

Let them vent

if it's too much to handle i will ask security to handle them for me, if not you just have to be calm nothing makes them feel more sadly and make up above them because everyone is from different background and they just don't know better.

I just calmer ask him or her, "why are you shouting at me?" "Is there a problem that we can work out together?"

I just ask the security to handle them