Generally, if it's not in my contacts list, then it's unsolicited and flagged spam. I won't answer unknown phone numbers (as I get a large number of spam calls in Spanish for immigration and high interest loans coming from or spoofed to the same area code and CO as my number, so even "local" numbers are suspect to me). If I don't answer, they leave a message, and it is someone or someplace I know about, then I'll add it to my contacts. If I answer an unknown number, just the act of asking "Hello?" seems to be about the equivalent as clicking an unsubscribe link in a true spam message; it notifies the spammer that they've got a warm contact that they can resell or contact again.

It's insane to me that you refuse to pick up the phone for people whose phone number you don't know. Aren't you anyone's emergency contact?

Yes I am. I know iOS allows someone to dial their emergency contact from a locked phone, so in that case I will receive a call from the person's phone that I know about. Otherwise, they leave a message and I get to it immediately and call them back.

The reality of an emergency situation where someone I know has me listed as an ICE contact and someone else calls on their behalf from an unknown number is that I cannot do much to help them in a situation that a minute or two of phone-tag would introduce. That's what 911 and other emergency services are for. If you are ever in a situation where you come across someone that has just sustained major injury, who are you going to call first? Their children or spouse to let them know of the situation, or medical help via 911? I'd hope you would chose the latter to get them the critical medical help they need before you inform someone else of the situation.

Additionally, if you're the emergency contact and I don't answer and you immediately call back, I'll probably pick up.

I don't normally block numbers, just let them voicemail me if I don't recognize it, but if a spammer will double-call like that I'll block them, and it means I'll pick up for emergencies.

Ditto for double-call signifying an emergency that I should pick up for, both for people I know and unknown numbers.

How can you block them? The whole point is that spammers call from unknown numbers. Double calling is just an annoying arms race.

Has anyone ever been double-called by a spammer? Honest question. I never have.

I suspect they're generally working on some pretty razor-thin margins with these things nowadays [1], and chasing someone who didn't twitch at the bait is probably a losing proposition for them.

[1]: Between all the easy competition and the incurred legal risks. Legal risk is a funny thing because you're basically rolling the dice on being able to collect money without getting in trouble. I wouldn't be surprised a full and honest accounting including legal risks yields a negative net expectation for phone spammers, it's just that even so, some people will get lucky and "win".

> Has anyone ever been double-called by a spammer? Honest question. I never have.

I have. Most of my spam calls have been of the "Rachel from Cardholder Services" variety - and while they usually dial from different numbers to give me the same damn spiel, a few times I have been double-dialed from the same number.

Both iOS and Android have various blocking methods, usually built into the OS.

They do not prevent the network from connecting to you, only prevent your device from triggering during the call, instead it will be silently ignored.

I do the same thing, unapologetically. In an emergency, I'll get a voicemail immediately after the call, tap once to play it, and call back. I'm not an EMT: if that extra 30 seconds matters, the number to call is 911.

If it's important they'll leave a message. I tend to check the message right away so if it's an emergency I'll know relatively soon.

It would be extraordinarily unusual for someone to have my number but not be able to call from the phone storing it. Anyone I'd be an emergency contact for, I have their number(s). There are theoretical problems with not picking up, but no practical ones that I've ever come up with or had suggested to me.

In an emergency situation do you think that everyone will be calling from their own phone? What about people who list you as a medical emergency contact or work emergency contact?

Do you expect that they wouldn't be either calling from their own phone, calling more than once, or leaving a voice mail? There are two people who I would lay money on knowing my phone number by heart, and only one of them lives within an hour of me. Everyone else will be stuck looking it up on their phone.

I often go out without my phone, have the ringer off, have a dead battery, or ignore the ringing because I'm driving. It's ridiculous to assume that I'm instantly available 100% of the time, or that I wouldn't treat different incoming numbers with different priorities.

There are websites for caller reputation. (If you can assume that an unknown number is suspicious).