A relatives' landline is easily 4+ a day.
I dunno why this can't be solved; 99% likely venality. I've solved it by telling my phone not to even ring if the number isn't in my contacts and periodically deleting all my voicemails unheard.
Everyone I want to talk to knows to text.
Phone companies make money from spam calls, so they have zero incentive to solve this.
In more general terms: marketing is a cancer, ruining every communications medium.
We do have a governmental agency (Bundesnetzagentur) where you can file complaints for spam calls and it seems to work.
In the last... I don't know how many years, I can only recall a single human-based phone call from someone not already on my contacts list (my apartment manager had a repair company contact me directly to schedule service).
The article doesn't say whether he was eg. a city-dweller inexperienced in the outdoors, but if he was, it might never occur to him that he was sufficiently lost to need outside rescue. As he said, he just "bounced around" between the trails until he found his way back. So he might have considered all the phone calls merely a distraction.