I would have thought so, but I read something about some payphones (presumably at the exchange) being limited to local calls only. You had to pay after speaking to the operator, and they could hear the coins going in (the 6d makes the bell ring once, the 1s makes it ring twice) so that you could hit the appropriate amount. But I've no idea if the coin-value is linked to any kind of balance-weight-timer thing. I can't see one, but it's hideously complex steampunk mechanics in there.