For those too young to know, call waiting is standard now your phone tells you when you get a call while on another call, but this used to be a paid upgrade feature and if you didn’t have it, the person calling you would get a busy signal (instead of ringing it would just beep) and you had no way to know.
We didn’t have call waiting, so for us it was literally just no using the internet before 9pm because you didn’t know who might call
For those too young to know, call waiting is standard now your phone tells you when you get a call while on another call, but this used to be a paid upgrade feature and if you didn’t have it, the person calling you would get a busy signal (instead of ringing it would just beep) and you had no way to know.