Both my wife and I are having an issue where our phones will connect to our vehicles via Bluetooth and immediately the car will think there is a call in progress to 10000000, that we have to forcefully end before normal operation.
I have a Moto Z3 and my wife has a Pixel3. The issue is happening with my Nissan Frontier and my wife's Kia Soul, and it started about a week ago.
The last firmware we go was 2-3 weeks ago so I don't think it is connected to that.
I have also seen other posts online that talked about apps like Skype or Tile being the cause but we don't have those installed.
I want to make sure that you are able to make and receive calls "hands free". That is a very important safety concern so I am glad that you reached out today. Are you devices having issues with any other Bluetooth connections? Have you contacted the car manufacturers to see if there is an upgrade to their software? Did Bluetooth work in the cars before the updates?
I have not looked into updates to the vehicles as they have no way to update without going to a dealer and having the software updated. Something changed on the phones or with an app on them that is triggering the issue.