Back in the 80's, criminal activity was divided up into "turf" sections through phone area codes.  The reason was because phone lines to land lines were done with wires.  This meant calls within the same area code weren't traceable.  Not easily anyway.  So Alex covered the 310 Beverly Hills region, Cheri, the Hollywood Madam later dubbed the "Death Row Madam" had the 213 area code as her turf, and Jody, the "High Tech Madam", managed the 818 area of the San Fernando Valley.  Every week or so the ladies would do lunch to discuss business and also give each other "bad numbers"  Serial killers were on the rise in LA at this time, and more and more women started going missing, especially prostitutes.