Weird outgoing phone call behavior

I imported the telephone directories from my wife's and my own phone to our 2015 Prius Four. Since most of the numbers are in our own area code, the area code is not specified if it is the same as ours. This afternoon my wife tried to call home (I was at home) and got the answering system for some business or other.

When she got home, I tried calling home from the car and got the same answering system, but when I reentered the phone number with the area code, calls went to our home number OK.

Is there a "default area code" in our car's system (or in all Prii's phone systems?) that needs to be overridden? I had reset everything, so it should not have been defaulting to the previous owner's area code.