Unfortunately today there aren't many cheap basic phone services. The cost-saving between measured use and flat rate is about $2-$3; this is the same actual dollar amount it was 30 years ago. But 35 years it was significant money -- between paying $4.65/month nad $6.65 a month.
More significantly are all the extra fees every subscriber must pay regardless of their service option. There's the "FCC line charge", perhaps a 911 fee, deaf service fee, universal service fee, line portability fee, portabello mushroom fee, etc. (Ok, you get my point).
Seriously, I had the barebest bones phone service you could get--measured rate party line, and they STILL had to put 2 ounces postage on the bill they sent me periodically with all the mandated junk printed on it.
As mentioned, some areas have discounted service, but I believe there are income eligibility requirements to receive this.