That's the point - all the people who said, "Not in contact list, do not pickup" (including me), did they think about an exception list?

I know I didn't. Short-sighted reaction after getting inundated with mandarin-speaking spammers.

I don't know what the globally correct answer is. But "never pickup" seems too extreme (even if the person, calling on the unknown number, leaves a voicemail, if you can't reach them with a return call, what then?)

Well at least where I live, the obvious exception to "don't pickup unknown numbers" rule is shipping services. Some of my online orders will arrive by courier and their drivers will call me when they arrive near my flat so I go out and pick my package. Completely unknown random numbers although companies do have the option to associate phone numbers with caller ID so I can see it's a delivery service. But by some reason (cost, convenience, no idea), they don't.

I can usually infer from the fact that I made an online order, sometimes they'll send me an SMS prior to sending but not always. Anyhow I did have my share of picking spam calls because of the necessity to ignore the "no unknowns" rule while expecting a package.

Overall I don't get that many calls yet that I'd have to configure the phone to reject ALL numbers not in the phone book. But call spam is definitely increasing, along with plain scam. I almost got my card stolen by a post office spoofing scam. And recently my bank cancelled my card and had to get a new one after someone from US tried to buy jewelry with it (I live in Romania) - probably leaked from one of the many online services I pay for. Now I switched to single-one-time-use cards from Revolut for all non-recurring payments, unfortunately it's too much of a hassle to do so for recurring ones. And with increasing security vulnerabilities my only protection is separate bank accounts and keeping only small amounts of money on the account linked to the debit card. No credit, only debit.