One has to get to grips with the archaic telephone system which was in place at the time. You have to put our present,modern technology behind you to appreciate how ancient the old system was. Don't even think about it when you're trying to fathom out what happened all those years ago,it was abysmal.
We've come a long way since then where there's no messing about,waiting to be connected ( via a voice ) it's all easy-peasy press-button. We know who's called,we also know who's ringing when the phone goes. Numbers are easily traced,etc etc.
It WASN'T a bit like that in the early to mid 80's.