I noticed the other day that voice control isn't 100%, duh.
Take for example, I wanted to navigate to Thackeray Lane. Even though I pronounced it with a "th" sound, it would pull up Zackary and fail at finding the road. I had to pronounce it with a "d" ("dackeray") to get it to pull up Thackeray.
This may or may not be fixable... but it also has a LOT to do with each persons way of pronunciation.
Since I was 3, I lost all hearing in my left ear. And that effects how I hear and speak. Mostly, the issue is that I'm usually louder than intended, but there are subtle "accents" in my pronunciations and probably "speech impediments" too (not significantly noticeable in everyday conversation).
But even for the general public, there can be similar "accents" that can cause the voice controls to fail sometimes.
So, if its picking up the wrong contact... there may or may not be a fix, ever.
On a side note, in the HR-V I had, when setting up speed dial option in vehicle, it allows me to record a voice clip of the name. Which was something I had to do because there were a couple of names that the voice "recognition" would always pick up as something else. So maybe the Tesla software might need something like that option.