“Would you prefer steak or fish?”*
“Yes.”
Look closer. Closer. There you go. That “yes” doesn’t mean you want both; it means you do indeed want steak OR fish.
If you’re implying that you would like both, the proper answer is below:
“Would you like to have a head massage or a neck massage?”
“No. AND.”
or just
“Both, please.”
There will be a test.
*Actually, my answer would be steak. I don’t like fish, so the point is moot. That’s why we’re asking YOU.