You may have missed a recent discussion on this newsgroup about how telephone props very often made the incorrect sound, such as ding-ding from coins in a single slot payphone, or a 300-type ringer on a 500 type phone. Characters dialing a phone call almost always dialed wrong, spinning the dial or dialing too few digits.
If a film made today is about an historical period, usually the phones will be wrong. It's common to have a black rotary 500 set with a clear plastic dial and modular cords as a phone in use in the early
1950s or even earlier. Other times a foreign old style set is used.I suspect virtually film viewer won't notice modular cords instead of hard wired or the wrong kind of pay phone.
As to modular connectors, I don't think they came out until the mid
1970s. When we got new phone service in 1972, our jacks were the old style big 4-prong. I believe my office converted to touch tone and modular sets around 1977, many of us continue to use that system to this day, though I think most of the WE 2500 sets have been replaced with more modern 2500 sets or modern fancy sets.