This phone may not be a carrier phone, but do you recall if any of your prior phones were from a carrier? (In the bad old days, you were almost universally required to get a phone directly from the carrier, at least until the Nexus was introduced.) If so, one of them might have synced over a preinstalled contact (which is why I suggested looking for one of these in your Google Contacts in the cloud, rather than on your phone).Lol.
This is not a cell phone carrier contract phone. So there is nothing pre-installed by the carrier.
It puzzled greatly me as well. My wife has an exact same phone bought a couple of months ago. No problem at all.
BTW, I totally understand if you'd rather just let this issue rest. If it doesn't interfere with your normal usage, then that's what's most important!