Local calls were unlimited in the 1970s and 1980s, like the are now. I think that this was true everywhere in the US but with different RBOCs perhaps some had different rules.
[0] https://www.techopedia.com/definition/4986/measured-telephon...
[1] http://articles.latimes.com/2012/jan/17/business/la-fi-lazar...
I remember calling my grandparents in Arizona cost 5¢ a minute, but calling relatives in the next city over—about 10 miles away—cost something crazy like 29¢ a minute.
This was in California. I'm sure the rate structures varied from state to state.