This is generally true, but...
In Switzerland calls from banks (and doctors and lawyers) don't submit numbers. That's due to secrecy laws (at least in the case of banks)
That said, in 45 years I never received a call from a bank.
Be careful about this. Scammers have bought Google adverts to advertise fake phone numbers for banks, so "ask Google what my bank's phone number is" unfortunately isn't secure against scammers.
I mean, yes, you need to independently source the official number; just make sure that your father knows how to do that and doesn't try to do it in a way which may be compromised.
Wiretapping the Secret Service Can Be Easy and Fun | Bryan Seely | TEDxKirkland
He has actual paper phone books, several address books, and spent some time as a naval signals officer ..
We're both of generations that have always been skeptical of infomation on computers ... I can't imagine life as someone who'd ask google what my banks number is.
> I myself have an additional rule that I always reject calls from unknown numbers
I'm highly skeptical of unknown numbers and they're almost always telemarketers or scam calls but ... my circle includes people who can lose phones, have batteries go flat, ask others to pass on a message, etc - fully whitelisting isn't always an option.