Fascinating thread.
My grandmother ran a post office in a rural area, which included telephone and telegraph services (and my aunt succeeded to the business retiring only a few years ago in her mid 80s, by which time, of course, everything had long been automated).
As a house involved with the communications industry (and I still have cousins working in this field, as did my father and grandfather both), the house had a wireless, in the days when batteries were 'wet' batteries, (this was nearly a century ago, back in the 1930s) and many in the village would assemble to listen to the commentary from a sports event being broadcast live on the national state radio service;
So, that house, an old building over 200 years old with incredibly thick walls, also stocked a wireless, and was equipped with telegraph, post office and phone exchange, while the office itself boasted a large, extremely solemn and accurate clock, with a second hand that gave an audible 'click' every time it crawled across the cream clock face……..I remember the old exchange as a very young child - some of these rural areas didn't get connected to the automatic system until the 1970s.
However, I do recall stories of the the long working days, and having to connect long distance calls, (including on Christmas Day - many people wished to make calls to distant loved ones on Christmas Day), and of never being able to 'switch off', as emergency services might need to be called, or urgent calls might have needed to have been made, sometimes at short notice….
As to how the calls were billed, I am not certain; however, the state phone company rented the lines and phones out, hence a flat rate applied. Indeed, when I was a child, local calls were also billed at a flat rate, irrespective of duration. Only long distance calls were billed by the minute.