Or the patient makes the mistake. I've seen it happen:

My wife has a foreign name--an English speaker coming at it cold is going to butcher it. Someone gets it right--either they've been told or they speak some Chinese. (It's not hard to say, but you have to know the Chinese Pinyin rules to get it right.) Over the decades we have grown used to responding to anything in the ballpark and then sitting back down if someone else responds. Oops--L shaped waiting room, we didn't see the somebody else. She ended up in back, the check caught it there.

Or look at my own name. That's the male spelling--but most people don't realize there is a male spelling. It's caused confusion over the years.