The new Google Pixel 6 phones are reportedly suffering from a phantom calling problem as evidenced by several complaints on Reddit and in independent testing. The majority of the cases point to the Google Assistant getting triggered and placing calls to random numbers. Right now, a temporary solution is to disable Assistant responses on the lock screen, but a fix from Google is on the way.
https://www.notebookcheck.net/Google-Pixel-6-phones-reportedly-phantom-calling-random-contacts-due-to-false-Google-Assistant-triggers.577559.0.html