I get this about once a month or so (I have to make a lot of phone calls for work). It’s always been one of my least favourite “jokes” that people tell me when I’m blocking on my name. To combat it, I say “no, I have a stutter” in a very serious voice, and usually it makes them deeply uncomfortable and quick to apologize. I find their discomfort sort of satisfying - it makes me hopeful that the next time they encounter someone blocking, they’ll think twice before making such an ignorant joke.