alt Hacker News> It was impossible, however, to convince my 99-year-old grandma to do the same; she vehemently refuses because that would be 'impolite'.
Assuming you can get access to their phone, only allowing calls from saved numbers would probably be the best solution, assuming she doesn't get random calls from hospitals and the like. If she's still using a landline though, that's a tough one to solve.
I can't just do that, she is an autonomous person, and quite willful also. Despite her age, she is not only as lucid as it gets - she still works (although from home) as an applied mathematician!