Changes

** The nature of mobile phone voice and data plans, and how these have evolved over time.

** Cellular connectivity in underground areas, such as subways (see some example events in https://timelines.issarice.com/wiki/Timeline_of_Bay_Area_Rapid_Transit) ✔

** tethering and hotspots created by mobile phones are worth mentioning, maybe in both timelines ) ✔

** '''Expansion started on 25 June 2019'''‎