Call and Text, the primary function of cellphones. Though we have smartphones, still are underpowered in usage.
People upgrade not of functionality but more on the latest model with few new features.
During my academic years in the 90s, few topics was covered on cell communication and I was taking night class sit in on antenna design with the basic Yagi design with my Electronic Communication friends.
But I got the chance to use beepers the size of post-it 2x3in or larger.
As they say in french
“Plus ça change, plus c’est la même chose.”
The more things change, the more they stay the same.