Junk calls and telephone scammers are a real problem for everyone (especially the elderly). Different personal situations require different countermeasures.
a predictive call blocker is one way. It automatically cancels computer
generated robo calls. Other calls from undesired numbers can be
individually blacklisted by you after they register on the caller ID. As
soon as you hook it up, your junk calls will be halved immediately. As
you block more and more other numbers, the unwanted calls will taper off
to almost zero.
[Note: My elderly mother couldn't properly block
calls, so I reviewed the incoming call list each time I visited.
Sometimes now it's a week before an unwanted number shows up.]
access, there is a White List Call Block that allows you to program in
the only numbers you want to allow (and all others are blocked). In addition, you can arrange with the phone company to require a code be entered before long distance can be successfully dialed each time.
Other situations might require you to have only a princess style phone that you have superglued the buttons on.
Another take on this is to have the carrier drop long distance service
at your loved ones home (1-800#s are still dialable).