Picture a quiet evening, a few minutes past nine. The dishes are done, the phone is face up on the counter, and it lights up with a number that begins with a plus sign. Not a ten-digit number with an area code you half recognize, but a plus, then two or three digits you have never seen on a screen before, then a long string of numerals. You have no friends abroad that you can think of. There is no delivery due. For a second or two the phone just buzzes against the counter, and you feel the small pull of curiosity that callers of every kind are counting on.
I have had that moment more than once, and what I have learned from it is mostly about what the plus sign does and does not tell you. It tells you quite a lot, in a narrow way. It does not tell you what you wanted to know when the phone lit up, which is who is calling and why, and the gap between those two things is the subject of this piece. I will take it in order: what the prefix is, why one prefix in particular misleads people, how a call can show a number that has nothing to do with where it began, and what I actually do about it.
A plus sign is a promise about the dial pad
The plus sign is shorthand. It stands for "dial whatever your country uses to leave the country, then continue". From a US landline that exit code is 011, and from many mobile phones you can hold down the 0 key to produce the plus itself. Phone software likes the plus because it is the same everywhere. Whoever wrote the number down can write it once, and any phone in any country can turn it into the right sequence of digits.
After the plus comes the country code, which is one to three digits long and is assigned to a country or to a shared numbering zone. After that comes the national number, in whatever shape that country prefers. A call shown as +44 20 7946 0000, which is a made-up example, begins with 44, the code for the United Kingdom, followed by a London-style area code and a local number. A call that begins with +91 starts with the code for India, and +52 is Mexico, +63 the Philippines, +234 Nigeria. You can learn a handful of these in an afternoon, and I do think it is worth learning a few, because an unfamiliar prefix gets dismissed or feared in equal measure, and neither reaction is useful.
What the prefix tells you is this: the number that was displayed on your screen belongs to that country's numbering plan. Because country codes are handed out so that different plans do not collide, it is an unusually clear piece of information. The one big exception is a shared zone like +1, which I get to below. What it does not tell you is where the person is standing, how long they have been there, which network actually carried the call, or whether the number on your screen is the number that really dialed. It describes a display. I come back to that word often on this site, and the reason is that a display is exactly what caller ID is, from the first digit to the last.
I should say, because it matters for tone, that I am not suggesting any country is a problem. Most calls from any of these prefixes come from ordinary people and ordinary businesses: family members, hotels, couriers, a friend who moved to Lisbon. Some of the largest customer-service operations in the world answer phones in countries you would not guess, and the people working in them are doing a job. If I ever sound as though a prefix is a verdict, take it as a failure of my writing and not as a rule of the numbering plan.
The prefix that fools people: +1
Here is the odd part. The prefix most likely to mislead you is the one that looks like home. +1 is not one country. It is the country code for the whole North American Numbering Plan, and that plan covers the United States and its territories, Canada, and a long list of Caribbean nations that share the same code and the same ten-digit format. A number beginning 876 or 809 dials exactly like a call across town, and so do 784 and 242, yet each of those codes belongs to a Caribbean country outside the US. The administrator of the plan, nationalnanpa.com, keeps the official list of what belongs where, and if you want to settle an argument about a code, that is the page to settle it on.
This is the setup for the one-ring scam, which also goes by the Japanese name wangiri, from the phrase for "one ring and cut". The mechanics are simple and a little cruel. Your phone rings once, long enough to register a missed call and not long enough to answer. You see a number that looks domestic, perhaps even a familiar-looking area code, and you call back out of politeness or curiosity. Because the number sits in another country, your call may be billed at international rates, and the person at the other end benefits from the minutes. Nobody had to break into anything. They only had to count on you being decent about a missed call.
The defense is almost embarrassingly plain. Do not return a missed call from a number you do not know, however ordinary it looks, and do not rely on the way the digits feel. If you want to check what a code covers, the number reader will tell you when a code belongs to Canada or to a country outside the US, and it flags toll-free codes (800, 888, 877, 866, 855, 844 and 833) and 900 premium-rate numbers, which have no home city at all. When it says a code is somewhere other than where the dial pad suggests, trust it over the dial pad. I wrote a longer comparison of the toll-free codes against local ones in four annotated calls, which is a good companion to this one if the 8xx numbers are what keep ringing on your phone.
One more detail that surprises people: your own contacts can fall into this trap too. A relative who works abroad might ring you from a +1 number in the Caribbean because a hotel or an employer provided it. You would not guess that from the digits, and you would not need to if the number were saved in your phone. It is another reason to keep your contacts tidy, and another reason why an unknown +1 deserves no more and no less caution than an unknown +44.
How a call can wear a number that isn't its own
Can a call from +44 really come from somewhere else? Yes, and the reverse as well, and the reasons are not all sinister. A person living abroad may keep a US number through an app and use it from another continent. A business may run a hosted phone system in one country and display numbers from three others, because each local number lets its customers call back cheaply. Internet-based calling made it easy to take a number anywhere on earth, and for most of the people doing that, nothing shady is going on. They are a student, an exporter, a family spread over two time zones.
It becomes a problem when the display is false on purpose. International routing adds more places where a call can be rewritten before it reaches you, and more borders across which nobody is checking. The industry's answer to false caller ID inside the US is a signing system called STIR/SHAKEN, which carriers are required to run under the TRACED Act of 2019. It helps one network vouch for how a call entered it. But it was built to verify caller ID on calls moving between US networks, which means it covers less ground for calls that begin abroad, and I would not read its presence or absence as a judgment on any single call. A signed call can still be unwanted. An unsigned one can still be your cousin.
The same logic applies to texts. A message from a +country number shows the prefix of the sender's number, not their location, and many businesses send texts through platforms that use entirely different numbers from the ones they call from. I gave that side of the story its own treatment in the piece on scripts for strange texts, so I will not repeat it here, except to say that the reading rule is the same: a prefix is a clue about the number, and the number is a clue about nothing in particular until you can check it somewhere else.
If you are wondering whether the prefix says anything about the kind of line, whether mobile, landline or internet, it does not, for the same reason an area code does not. The country code identifies a numbering plan, and each plan assigns blocks of numbers to providers without labeling the technology. I spelled out why in the short briefing on line types, and the conclusion is as dull as it is useful: the digits carry the place a number began, nothing else.
What I do when the plus sign shows up
I do nothing, at first, and that is a deliberate choice. There is almost never a reason to hurry. A real call usually leaves a voicemail with a name and a reason, and the ones that matter get repeated, often by text or by an email that you can verify. So the phone rings out, and while it does I ask myself two questions. Do I know anyone abroad, or am I expecting a delivery, a hotel, a visa office or a relative on a trip? If the answer is yes, the call may be exactly what it looks like. If the answer is no, then the plus sign is the least interesting thing about it.
If no message arrives, I do not call back. I do not press digits when a recording asks me to, because pressing a key tells the system a live person is on the line. If a message does arrive and claims to come from a bank, a courier or an agency, I check the claim at its source, which means a number printed on the card in my wallet or on the organization's own website, not the one the caller gave me. And if the call looks like a scam attempt, I file it at ReportFraud.ftc.gov, and forward any spam text to 7726 (SPAM), which hands it to the carrier. It takes a minute, and it is the only part of the whole business that leaves anything behind for the next person.
Sometimes I have a perfectly good reason to ring a country back, because a friend has moved or a business abroad has written to me. Then I dial the plus sign, or 011 from a landline, followed by the country code and the number, and I check my plan's international rates first, since they can be high on some plans and trivial on others. I only do this for numbers I have reason to trust, which in practice means numbers that came to me through a channel I already knew.
When the calls are constant, the thing to do is look at them as a set instead of reacting to each ring. A steady stream from overseas prefixes is a pattern, and reading it calmly is a skill, which I laid out step by step in the call history walkthrough. If the calls are simply a nuisance, your phone can quiet them. On an iPhone, Settings > Phone > Silence Unknown Callers sends numbers outside your contacts to voicemail, and on Google's Phone app, Phone > the three dots > Settings > Blocked numbers lets you block specific ones. Your carrier may also offer a setting that restricts international calls on your own line, so it is worth asking whether yours does. The FCC's consumer pages describe the complaint route if the calls cross the line from annoying to abusive.
I have come to like the plus sign, oddly. It is one of the few things on a caller ID screen that is exactly what it claims to be: a statement about a numbering plan, made in a notation any phone on earth can read. It simply was never a statement about the person. Once you hold those two ideas apart, the evening call stops being a small mystery and becomes what it nearly always is, a number on a screen, waiting for you to decide whether it has earned a reply.