I was in a Subway a couple of months ago and someone ordered an iced coffee - he was handed a hot coffee with an ice cube in it. It still makes me laugh.
I've actually done similar, I was covering the tills in a cafe and someone asked for a white tea, not knowing white tea was a thing I got them a milky tea. They sent it back and got a refund.
Long time ago in Newcastle I ordered a bacon and avocado sandwich expecting cold crispy bacon and avocado slices and got a hot bacon butty with guacamole. Was lush.
I was in a Subway a couple of months ago and someone ordered an iced coffee - he was handed a hot coffee with an ice cube in it. It still makes me laugh.