We ran out of Grande cups so had to use Venti cups for the rest of the day, until the delivery came the next day. Everybody understood - some a little confused at first, some thought they were getting a free upgrade - but not Helena from Hell (not her real name and presumably not her address) who really couldn't compute the concept.

The customer - let's call her Helena - orders an extra hot Cappuccino in Grande size, that is her regular drink she always gets. Upon ordering she was informed (like everyone else) that it would come in a larger cup but the drink volume will be the same. The reason why was explained: "unfortunately we ran out of Grande cups". Not a difficult concept to comprehend.

Despite always getting the same drink at the same price. All of a sudden the customer thinks she has been overcharged. It is just a larger cup! But the customer is super aggressive and extremely vocal, witnessing this you would have assumed I offended all her ancestors.

I even did a demonstration with plastic cup sizes to demonstrate the volume, absolutely didn't understand it at all.

Went through the Tall, Grande and Venti pricing on the till to confirm the price hasn't changed... Helena, not convinced, the cup is larger. Physically larger, must cost more. After a little back-and-forth... various compromises... perhaps the cup is too large? I guess some people may feel intimidated by large cups? Offered the drink in Tall (yes, the name didn't help). No, that is smaller than what she normally has. How about two Tall cups instead of the Grande cup we don't have? No additional charge. No it is still smaller than what she normally had. How about just an upgrade to a Venti at no extra cost? OMG, back to the overcharging her for a bigger cup size than she asked for.

Just give her a refund and be done with it? If only that was the solution... "I want my cappuccino grande, extra hot, what's so f**king hard to understand? are you thick?" Excuse me?

We get customers like this often. They have a quick assumption to a problem and they stubbornly hold on to their misunderstanding, they explode expressing their dissatisfaction and no matter how calmly you speak to them, they don't listen and reconsider the facts. When they are unwilling to accept a refund as a conclusion solution it traps us into an difficult situation.