A lot of elderly have NO broadband.
Just a POTS line, and pay for all non-local calls.
(Or all calls, in some cases)
They already pay in excess of $60/month just for the POTS service.
(My mother is one in this category)
I can see where the OP is heading!
Depends what kind of "POTS" line they have...
it might be "POTS" off an ONT or BASEBAND IP in which is pots emulated into SIP - In which case a better deal on tolls could be on the table
Or it might be a NEAX connection which is a traditional circuit switched telephone line which case no deals on tolls will be on the table