We had one of these in my mom's car in the early 90s in SoCal and it was also cellular one. Her plan only had a handful of minutes a month, it was really just in case we had car trouble and needed to call AAA. At the end of the month we got to use up the 15 minutes or whatever it was. I remember calling my grandma while were driving to her house and the entire conversation was just, "Grandma! I'm in a car and I'm talking to you!".