Update - Outbound calls I didn't make in call history.

After unplugging the phone jack in the alarm system box, once again, for the 6th Thursday in a row, at 1:22am,  my phone made an outgoing call to 855-294-2278.   I guess I'll make another call to Cox.  Maybe whoever I reach will have something new to suggest, other than switching out the modem.   Thanks to all for the ideas I've gotten from the replies to my original post.