In 1920 long distance calls were charged by the minute, and by the distance. The operator would write down when she connected your line on the switchboard, then note down the time when she unhooked it.
In 1920:
>a call from New York to Indianapolis, Indiana would cost $4.15 for the first three minutes and $1.35 for each additional minute
>a call from New York to Los Angeles, California would cost a lot more - $15.65 for the first three minutes and $5.20 for each additional minute.
In Germany during WWII (according to Richard von Rosen's memoir) you had to wait a few hours for your long-distance call to connect. You could pay double to get connected faster and ten times the price to connect faster still.
From what I recall from the 1970's, we paid a monthly charge for each line (number), phone rental (each), and then long-distance calls were itemized. If you had two phones in your home for the same line, you'd be charged an additional location fee, as well as the rental for the second phone. If you had two numbers (like one for the parents and one for the teenagers) then it was 2 lines, 2 phones, plus any long-distance calls each month.
By that time their billing was computerized, so the monthly statements would list each long-distance number you called and how many minutes you spent talking. I was calling BBS's at that point (300 baud acoustic coupler hotness!) and I had a phone budget that I had to stay under or pay the parents. Long distance calls (basically anywhere outside your city) were expensive!
Bell planned for the 2 line scenario, as your wiring out to the pole had red/green (tip + ring for line 1) then black/yellow pairs (tip + ring for line 2). So they could offer two lines without needing to run additional wires to the house. Or use the second pair if the first one went bad. The Bell System did forward-thinking like this all the time. And could afford it because (as mentioned) they amortized their system investment over 40+ years.
One of the elements that came with mechanical (as opposed to human-powered) phone exchanges was introduction of "impulse billing" (there's probably a proper term for it) where establishing a connection triggered a device that printed a symbol every "pulse" from the timer on a ticker tape. This would be then collected, pulses counted, and you'd be billed based on the amount of those pulses. Similarly different devices would be able to generate "logs" of actions like "connected line A to line X", which would be collated and sorted regularly.
Different billing strategies often were based on how often the pulse was triggered. This is also related to "billing by the second" - it was originally a technological issue that caused per-minute billing.
Yes, at first it was an analog process with toll tickets making their way to your local business office who would prepare your bill, eventually it went to tabulation technology (punched cards) and then into the 1960's computers.
As far as the bill - you'd be billed for local service (either unlimited or metered rate), plus a phone rental, and then on top of that local toll and long distance usage. For this, you got a telephone, and the phone company was responsible for your inside wiring as well.
It was so capital intensive that it must have been earning good money, but without computers, how was their business model?
E.g. a fixed fee per line, or did they have a way to charge its customers per call, or duration of the call as we're now used to?