Looks like they are going the way of the pay phone as well.
https://en.wikipedia.org/wiki/Call_box
Decline in usage
In California, freeway callboxes were used about 98,000 times in 2001. That number dropped by 80 percent to 19,600 times in 2010, or about 1 call per box per month. The cost of callboxes for the Service Authority for Freeways and Expressways (SAFE) program in the San Francisco Bay area is $1.7 million annually. As a result, since 2009 approximately half of the callboxes have been removed from certain California highways, preferentially leaving them only in places where cell phone coverage is poor.
Florida previously had callboxes installed at one-mile intervals along all its
Interstate Highways as well as
Florida's Turnpike. These boxes were all removed by 2014 after a 65-percent decrease in usage over an eight-year period, in line with increased mobile phone usage. The boxes were costing the state roughly $1 million per year to keep operational.