Dialing 503-555-1212? Or any three-digit-prefix-555-1212? This pre 4-1-1 information line. Before that you had to call 0 to get an operator for assistance.
Or writing down phone numbers as (503)555-0110? That, for those that haven´t had the pleasure of knowing you could just dial seven digits. And earlier five or four digits. But life got more complex, or too numerous, for the earlier times. All the way back to calling the operator and asking for who you wanted. Small exchanges in those days.
I´ve wondered about phone numbers. How long will the pool of them persist? Before we have too many unique places to call and there is no longer an available number. Like IPv4, it is inevitable for us to outgrow the system.
Or being able to call a number, wait for the answer, and hang up quickly to not be detected. But that´s a different set of memories to follow in another post.