I'm talking about full-on yelling/telling off someone working in a shop over some sort of issue?
I was waiting for a script at the chemist today and there was a woman at the prescription counter with an elderly man (who it seemed the medication was for) and she was making a massive scene, yelling at the pharmacist. The pharmacist kept his cool and didn't seem to get ruffled, but she was highly confrontational. I overheard her saying something about a mistake made previously, and stating that she didn't want to have to come back to the pharmacy over the weekend.
It got me thinking - have you ever really 'lost it' in a shop/business scenario? If so, do you feel your actions were justified, or do you look back and wished you'd kept your cool?